Advice needed for H1-B Transfer

Hi all, I’m currently working as a data scientist at a US company, and have just received an offer for Founding AI Engineer for an AI startup (funded by Y Combinator). I’m on my H1-B visa.

I got the offer letter too. Should I start the H1B- transfer process with YC first, and not inform my current manager of my plans yet? Is it better to get the H1B transfer petition first , before resigning from my current company? What is the ideal time to resign from current company, from immigration POV?

Please advice. Thank you!