The references mentioned in this answer to the Kundalini Concept are based on the Smartha concept and inclined to Shaivism. Is there any comment or reference to such a concept in the Pancharatra Agamas/ Vaishnava Agamas or anywhere in Vaishnavism?
The Concept of Kundalini is not actually alien to Vaishnavism. But as the Kundalini is associated with meeting of Shakti with Shiva, So, Vaishnava Puranas have only very few refrences regarding it.
For eg. Srimad Bhagvatam describes how Sati Leaves her body by raising pranic force (Kundalini) to headregion and leaves her body:
इत्यध्वरे दक्षमनूद्य शत्रुहन्क्षितावुदीचीं निषसाद शान्तवाक् । स्पृष्टा जलं पीतदुकूलसंवृतानिमील्य द्दग्योगपथं समाविशत् ।। कृत्वा समानावनिलौ जितासना सोदानमुत्थात्य च नाभिचक्रतः । शनैर्ह्र्दि स्थात्य धियोरसि स्थितं कण्ठाद्भ्रुवोर्मध्यमनिन्दितानयत् ।। एवं स्वदेह महतां महीयसा मुहुः समारोपितमंकमादरात् । जिहासती दक्षरुषा मनस्विनी दधार गात्रेष्वनिलाग्निधारणाम् ।। ततः स्वभर्तश्चरणाम्बुजासवं जगद्गुरोश्र्चिन्तयति न चापरम् । ददर्श देहो हतकल्मषः सती सद्यः प्रजज्वाल समाधि जाग्निना ।। [S.B. 4.4.24-27]
O annihilator of enemies, while thus speaking to her father in the arena of sacrifice, Satī sat down on the ground and faced north. Dressed in saffron garments, she sanctified herself with water and closed her eyes to absorb herself in the process of mystic yoga. First of all she sat in the required sitting posture, and then she carried the life air upwards and placed it in the position of equilibrium near the Nabhi Chakra [Manipura Chakra]. Then she raised her life air, mixed with intelligence, to the heart [Anhata Chakra] and then gradually towards the pulmonary passage, to the throat [Visuddha Chakra] and from there to between her eyebrows [Ajna Chakra]. Thus, in order to give up her body, which had been so respectfully and affectionately seated on the lap of Lord Śhiva, who is worshiped by great sages and saints, Satī, due to anger towards her father, began to meditate on the fiery air within the body. Satī concentrated all her meditation on the holy lotus feet of her husband, Lord Śhiva, who is the supreme spiritual master of all the world. Thus she became completely cleansed of all taints of sin and quit her body in a blazing fire by meditation on the fiery elements.
It is surely a description of Kundalini Yoga because it gives the name of all places where Chakras are mentioned.
Particularly it also states:
कृत्वा समानावनिलौ जितासना सोदानमुत्थात्य च नाभिचक्रतः ।
Then she carried the life air upwards and placed it in the position of equilibrium near the Nabhi Chakra/ Navel Chakra [Manipura Chakra.] (S.B. 4.4.25)
As it directly uses the name Nabhi Chakra. It is a sure refrence for Kundalini rising.
Moreover Prabhupada in Commentary of Srimad Bhagvatam 4.4.25 states
The yogic process is to control the air passing within the body in different places called ṣaṭ-cakra, the six circles of air circulation. The air is raised from the abdomen to the navel, from the navel to the heart, from the heart to the throat, from the throat to between the eyebrows and from between the eyebrows to the top of the cerebrum. That is the sum and substance of practicing yoga. Before practicing the real yoga system, one has to practice the sitting postures because this helps in the breathing exercises which control the airs going upwards and downwards. This is a great technique which one has to practice to attain the highest perfectional stage of yoga, but such practice is not meant for this age. No one in this age can attain the perfectional stage of such yoga, but people indulge in practicing sitting postures, which is more or less a gymnastic process. By such bodily gymnastics one may develop good circulation and may therefore keep one’s body fit, but if one simply restricts oneself to that gymnastic process one cannot attain the highest perfectional stage. The yoga process, as described in the Keśava-śruti, prescribes how one can control his living force according to his desire and transmigrate from one body to another or from one place to another. In other words, yoga practice is not meant to keep the body fit. Any transcendental process of spiritual realization automatically helps one to keep the body fit, for it is the spirit soul that keeps the body always fresh. As soon as the spirit soul is out of the body, the material body immediately begins to decompose. Any spiritual process keeps the body fit without separate endeavor, but if one takes it that the ultimate aim of yoga is to maintain the body, then he is mistaken. The real perfection of yoga is elevation of the soul to a higher position or the liberation of the soul from material entanglement.
Thus above commentary by Vaishnava Acharya also shows, Kundalini is not alien to Vaishnavism.
I also found this verse on Shristi Khanda 34.249 of Padma Purana:
Then they should meditate on the image of preceptor on Sahasrara with a white garment and a sacred thread and white flowers and cloths and with white sandal should go out of (village) to a river and perform daily routine carefully.
Padma Purana Bhumi Khanda chapter 53 also states:
It remains unsteady in the middle part of the palate. There remain (the two vessels of the body called) Ida and Pingala and the artery called Susumna. Due to the great power of it only, there is indeed the itch for sex in the cage formed by the net of arteries, in the case of all beings. O messenger, the organs of generation of the male and also of the female throb.
As a Side Note I want to mention that in some recensions of Mahabharata, Uttara Gita is found where Lord Krishna teaches some concepts of Kundalini to Arjuna. A commentary on Uttara Gita by Sri Gaudapada is also avaliable.
No, The concept of Kundalini is not at all alien to Vaishnavism.
Narada Pancharatra, A highly respected text in Vaishnavism, has chapters dedicated to the very concept. Some relevant excerpts are provided below:-
Narada Pancharatra, 5.10.9-10
The effulgent svayambhu-linga, which is as brilliant as millions of suns, which spreads the network of desire, and which is triangular in shape, is situated within the muladhara-cakra.
Above the muladhara-cakra is the place of the kama-bija, within a dot. Above this, the kundalini-sakti, which is a manifestation of the Lord, is situated.
Narada Pancharatra 5.10.23-28
Now I have told you all about the Yogas that have no comparison. First perform the Puraka yoga and concentrate your mind in the Muladhara plexus.
Next arouse the Sakti that exists between anus and the origin of the lingam(organ of generation). Carry it through the several plexuses to the Bindu-cakra (i.e. the thousand petalled lotus).
Consider there Siva and SivA, the highest Sakti as one and the same. Here originates a nectar like juice of the nature of the juice of Lac.
Then make that Krsnaa Sakti, capable to grant success in Yoga, drink that immortal nectar. Then satisfy the Devatas of the Six Cakras also with that nectar. (27) Thus the intelligent devotee is to practise this path of Knowledge and control every day his VAyu (breath) in the MuladhAra lotus (Sacral plexus.)
Thus he will be free from old age and death and this bondage of Samsara. Moreover all the mantras that turned out before as defiled, yield now the Siddhis.
Furthermore, Narada Purana, well-revered as a Vaishnava Purana also mentions Kundalini Yoga.
Narada Purana III.65.66-71
Thereafter, the wise disciple should conceive that as his own atman free from impurities. It has been washed with the continuous flow of nectar from the lotus feet of the guru. He should meditate that the mulavidya is flowing along the path from muladhara to brahmarandhra. In the circular disc of the air, just below the muladhara there lies the vayubija. By means of the air born of the seed of the air, one should go to the triangular shaped location of the fire and by means of the fire born of the fire-sced lying there, one should awaken Kulakundalini as stationed in the muladhara in the form of a sleeping serpent coiled round the svayambhulinga. She should be meditated upon as subtle like the thread of the stalk of the lotus. It has the lustre of ten million lightenings and is very subtle. Thus meditating on her one should awaken her by means of Kurcabija hum. In accordance with the method as given by his guru, the wise man should take her (kundalini) to the brahmarandhra along the path of susumna while piercing the six cakras.
As per this webpage, ahirbudhnya-saṃhitā has below descriptions about kundalini:
It contracts itself into the form of the world and is therefore called Kuṇḍalinī ; and it is called Viṣṇu-śakti because it is the supreme power of God.
By fourteen efforts there come the fourteen vowels emanating through the dancing of the serpent power (Kuṇḍalī-śakti) of Viṣṇu. By its twofold subtle power it behaves as the cause of creation and destruction. This power rises in the original locus (mūlā-dhāra) and, when it comes to the stage of the navel, it is called paśyantī and is perceived by the yogins.
Round the nābhi-cakra there exists the serpent (kuṇḍalī) with eight mouths, stopping the aperture called brahma-randhra of the suṣumnā by its body
The suṣumṇā has five openings, of which four carry blood, while the central aperture is closed by the body of the Kuṇḍalī.
lakshmI tantra ch. 26 verse 15 also talks about kundalini:
15 - Now listen to the description of the shaktI known as kundalinl, which contains the entire creation in a coiled (i.e. concentrated) form and which is identical with shabdasakti.
Gautamiya Tantra, A highly respected Vaisnava tantra among Gaudiya Vaisnavas mentions Kundalini Yoga several times and holds it as the means leading to mantra-siddhi as well as liberation from the bonds of samsara.
Gautamiya Tantra Chapter 7
In the Final Chapter, the whole process of Kundalini Yoga along with a detailed description of chakras etc. is described. Here are some excerpts:-
Gautamiya Tantra Chapter 32
As for acharyas, saint Jnaneshwar from the Varkari Vaishnava Tradition mentions it explicitly in his commentary on Bhagavad Gita 18.52
The power ‘Kundalini’ (kuṇḍalinī) then is aroused (becomes active) while the way to Madhyama, also called Sushumna (suṣumnā) the particular passage in a human body said to lie between ‘Ida and Pingala’ (iḍā-piṅgalā—two other air-passages in the body), is made clear and widened and then the life-winds rise and ascend up, piercing through all the six wheels viz. from the Muladhara to the Ajani (agni).
Then there descend from the cloud in the form of the thousand-petalled lotus (in the region of Brahmarandhra in the seventh wheel) copious showers of ambrosia which flow down straight and reach Mulabandha. Thus he, the seeker, serves on a plate cooked food of mixed com (rice and pulse) in the form of the mind and the life-winds, to the terrible deity of sentience (cid-bhairava) dancing on the mountain (Kailas) in the form of the region of the Brahmarandhra.