Almost no one believes that the soul originates from Brahman. First of all, the six main Astika or orthodox schools of Hindu philosophy don't believe it:
Samkhya: As I discuss in this answer, the Samkhya school didn't even believe in Brahman; they thought there were only two kinds of entities in the Universe, Purushas or souls and Prakriti or matter. And they didn't think that Purushas originate from Prakriti; they thought that Purushas are eternal, as Gaudapada says in the Samkhya Karika Bhashya:
Here, the Manifest is caused; the Unmanifest is uncaused; so is the Spirit uncaused, because it is not produced. The Manifest is non-eternal; the Unmanifest is eternal; so also is the Spirit eternal.
Yoga: The Yoga school did believe in the existence of a special Purusha called Ishwara, but apart from that they shared the general worldview of the Samkhya school, including the eternality of souls.
Nyaya: The Nyaya school also believed that the soul is eternal, as Vatsyayana says in the Nyaya Sutra Bhashya:
The Soul, which has been proved to be something different from the Aggregate of Body etc., - is it eternal or non-eternal? "Why should there be a doubt on this point?" The doubt arises from the fact that both are seen; that is to say, things known to exist are of both kinds, - some eternal and others non-eternal; so that it having been proved that the Soul exists, the doubt remains. The answer to the above question is that those same arguments that have proved the Soul's existence also go to prove its previous existence, as is clear from the modifications undergone by the body; and this Soul must exist also after the perishing of this body.
Vaisheshika: The Vaisheshika school also believed that the soul is eternal, as Shankara Mishra says in the Upaskara:
As there is no proof for the supposition of parts in the ultimate atom of Air, and thus Air is eternal, so also in the case of the Soul.
Purva Mimamsa: The Purva Mimamsa school was divided on the existence of Brahman, but regardless they didn't think the soul originated from Brahman. Those that do believe in Brahman just consider Brahman to be yet another soul.
Vedanta: The Vedanta school also believes that the soul is eternal and does not originate from Brahman, as Vyasa says in Adhyaya 2 Pada 3 Sutra 17 of the Brahma Sutras:
nātmā āśruternityatvācca tābhyaḥ
The individual soul has no origin; because the Upanishads do not mention this, because its eternality is known from them and (because of other reasons).
Now there are couple minor sects of Hinduism that do believe that the soul originated from Brahman. First of all, some members of the Shaiva Siddhanta sect. There are three kinds of Shaiva Siddhantins. There are mainstream Shaiva Siddhantins, who follow Meykandar and reject the Vedanta school. They think the soul is eternal. There are Shrauta Shaiva Siddhantins, who follow Srikantha Sivacharya and Appayya Dikshitar and follow the Vedanta school. They too think the soul is eternal. And then there is the Saiva Siddhanta Church, an organization which thinks that the soul originates from Brahman. Here is what a book published by the Saiva Siddhanta Church says:
God Siva created the soul. How did he do this? Was it like a potter shaping clay into a pot? Was it like a carpenter creating a house out of lumber? It was more like the tree. In order to create another tree, the tree sends out its branches and the fruit grows on the branches and the seed grows within the fruit. The fruit drops off and the seed sprouts and a shoot comes out; that shoot becomes a twig, then a sapling, then a small tree, and then a large tree. Finally, the tree is fully matured and sends out its fruits and begins the process all over again. In a similar way Lord Siva has created individual souls. Saint Tirumular assures us of this in one of his many statements about Siva the Creator: Of yore He created the worlds seven, Of yore He created celestials countless, Of yore He created souls without number, Of yore He created all-Himself, As Primal Param, uncreated. TANTRA TWO VERSE 446
Also, there is some indication that some at least Shaktas believe that the soul originates from Brahman. As I discuss in this question, the Dvaita philosopher Madhvacharya characterizes Shakta beliefs in this way in his Brahma Sutra Bhashya. Baladeva Vidyabhushana and Nimbarkacharya say the same thing in their commentaries on the Brahma Sutras. But I'm not sure how much truth there is to that, or which Shakta sect they're referring to. It's also worth noting that Adi Shankaracharya accuses the Pancharatra Agamas of saying that the soul originates from Brahman, but Yamunacharya's Agama Pramanya and Ramanujacharya's Sri Bhashya present detailed arguments against this interpretation of the Pancharatara Agamas, as do the works of some Advaitins.
Also, you asked about the soul merging into Brahman. All the non-Vedantic Astika schools, and most Vedantic philosophies, think that the soul still exists as a distinct entity after attaining Moksha. Advaitins don't think that, but then again from an absolute perspective they think that Brahman was always the only thing that existed. The only Vedantic philosophy which thinks that the soul really does exist as a distinct entity now, but will no longer exist as a distinct entity after attaining Moksha, is Bhaskaracharya's philosophy of Aupadhika Bhedabheda. Bhaskaracharya believed that the soul was Brahman limited to an Upadhi or constraint, and upon the attainment of Moksha, the Upadhi goes away, so the soul which attained Moksha no longer exists as a distinct entity, all that's left is the unconstrained Brahman. Now Bhaskaracharya's commentary hasn't been translated into English, but you can find out more about his philosophy from this book by P.N. Srinivasachari. Also, just as the Saiva Siddhanta Church thinks that the soul originated from Brahman, they also think the soul merges back into Brahman upon attaining Moksha.