iPad (7th gen) randomly goes to lock screen

Hello,

I bought a 7th generation iPad (just "iPad", not Air, Pro, or Mini) a few months ago and it will randomly go to the lock screen every 20 minutes or so. It doesn't seem to matter what app I'm using, and the intervals are random/unpredictable. It doesn't completely turn the screen off - it just goes straight to the lock screen, as if I'm waking it up.

I'm running iOS 14.1, but this has continued to happen after multiple OS updates since I bought it back in May. I've done all the basic troubleshooting, such as a hard reset, iOS update, etc. and some relatively exhausting internet searches on the topic. The only thing I haven't done is a full factory reset (as I'm understandably trying to avoid doing this). The iPad has not been dropped, suffered water damage, or anything of that sort. I bought it new and it hasn't really left my bedroom since I got it.

Also, it might be worth noting that the screen brightness has started randomly changing, and Automatic Brightness is most definitely turned off. This happens probably about as often as the random lock screen thing, but I haven't noticed if they both happen at the same time or not (I'll pay attention to this in the future).

I suppose this is a relatively minor annoyance, but it does get pretty irritating when I'm in the middle of an online/multiplayer game. Any thoughts?