iPhone bugging out continuously

Hi, idk if anyone else is having this issue since the new iOS 15 update, but my phone is completely bugging out. I’ve had the iPhone 12 since January of this year - so it’s still quite new - and over the past few days it’s just acting up. I updated to the newest iOS 15 last Saturday, then on Friday apps would close randomly, if I was editing video content - for uni - it wouldn’t download unless I restarted the app or phone a few times, or the screen would just completely shut down before opening back onto my lock screen. It’s been updated to iOS 15.1, so I don’t think it’s needing updated…

any ideas or help? It’s currently switched off, to see if that helps