YouTube has an inactivity timer that will pause your videos if it has detected, or inactivity. Only thing I can suggest for you is to go into your YouTube settings and try to increase or disable the inactivity timer.
The same thing on my brand new Galaxy S24 Ultra. It pauses in random time intervals, in 5 minutes, in 25 minutes, in 2 minutes. And sometimes it plays smoothly in a few hours at the same network and the same environment independent of charging or not. So it's definitely not an any YouTube settings or phone settings. It looks like some memory optimizer effect or something like that. I've tried to add YouTube to any exclusions, make it unrestricted for memory optimizer and background task optimizer without any result. It's really annoying to tap you screen to keep youtube playing multiple times watching single video.
