Pixel 5 keeps restarting, how can I repair/diagnose it?
A few months ago my phone kept restarting every 2-20 seconds for an hour straight. After it stopped I suspected it was a heat issue as it was a really hot day. But today it's been doing the same thing for about 80 minutes (and still does it) and the exterior temperature is pretty cold (20C inside, 10C outside). I noticed that right before it started restarting, the power menu kept popping up a few times, so for that reason alone I suspect it could be something about the power button being broken or something. But to my layman's eyes it seems to click fine and doesn't look loose or pressed, so I don't know.
If I hold the power button down nothing seems to change - it keeps restarting. And if I hold the power and volume down button down it enters the boot menu for a few seconds and then just restarts again.
I've dropped it on wood and linoleum (without a cover) a few times in its lifetime so perhaps it has some interior damage but there's only a few scratches on the outside and no cracks or anything like that - but nothing recently.
Any help is appreciated
EDIT: Now it's completely drained of battery from restarting so much and now it's just flashing the battery icon every few seconds as if I'm manually trying to turn it on and off all the time, so I suspect it's definitely something related to the power button