Krishna and Rama were born to humans by taking birth from womb. What about Shiva?
Yes, according to Shiva Mahapurana, Satarudra Samhita Lord Hanumana and Sage Durvasa are the incarnation of Lord Shiva and they have taken birth from the womb of Anjana and Anusuya respectively.
Lord Hanumana birth is described as:
तद्वीर्यं स्थापयामासुः पत्रे सप्तर्षयश्च ते। प्रेरिता मनसा तेन रामकार्यार्थमादरात्॥ ५॥
तैर्गौतमसुतायां तद्वीर्यं शम्भोर्महर्षिभिः। कर्णद्वारा तथाञ्जन्यां रामकार्यार्थमाहितम्॥ ६॥
Like a person suffering from lust, Siva at the instance, the saptarsis, (the Swan sages) carried the semen of Siva, for the purpose of Šrī Rāma, with respect, over the tree leaf and inserted the same in the ear of Anjani the daughter of Gautama, through ear to her Womb.
And Sage Durvasa birth is described as:
अथ ब्रह्मा हरिः शम्भुरवतेरुः स्त्रियां ततः। पुत्ररूपैः प्रसन्नास्ते नानालीलाप्रकाशकाः॥ २४॥
Thereafter Brahma, Visnu and Siva, were born as sons from the womb of Anusuya, who were delightful at heart and performed several Sports.
विधेरंशाद्विधुर्जज्ञेऽनसूयायां मुनीश्वरात्। आविर्बभूवोदधितः क्षिप्तो देवैः स एव हि।। २५॥
Moon was born of the womb of Anusuya from the amsa of Brahma, but since the gods threw him in the ocean, he emerged out of the same (at the time of the churning of the ocean).
विष्णोरंशात्स्त्रियां तस्यामत्रेर्दत्तो व्यजायत। संन्यासपद्धतिर्येन वद्धिता परमा मुने!॥२६॥
From the aniisa of Visnu, Datta was born from the Womb of Anusuya. O Sage, he propagated the best method of Sannyasa.
दुर्वासा मुनिशार्दूलः शिवांशान्मुनिसत्तमः। जज्ञे तस्यां स्त्रियामत्रेर्वरधर्मप्रवर्तकः॥ २७॥
O Excellent sage, from the ansa of Šiva, Durvasa, the propounder of dharma and the best of the sages was born.