I had this EXACT same problem after trans fluid got above 150* F. Its a 4l60e in 1997 silverado 4x4.
It ended up being the TCC solenoid was leaking fluid past it when commanded ON once it got warm. The seam in the snout from manufacturing split and would close back up when it was cold.
Of course you'll have to change the whole wiring harness in the transmission to fix this as the TCC solenoid is the only solenoid in a 4l60e without a connector on it, that is its directly wired to the harness unlike the shift solenoids.
This is that little bastard.
https://m.imgur.com/gallery/wWkLiTG