First Boot Loop, then: Face ID, Auto-Brightness, Proximity Sensor, True Tone all Stopped Working

Is my iPhone XS Max about to die or something? Phone was sitting on my dresser and then I noticed it was in a boot loop. About an hour of trying to fix it without success, I was able to shut it off. About 2 hours later I went to turn it back on and it started to work again but the auto brightness was acting weird. Kept dimming and brightening the screen every 30 seconds. Force restart and it fixed it... for a little while. I update to IOS 15, no issues for about 2 days. Again, phone just sitting on the table and randomly get an alert that my Face ID is disabled and "unable to activate." Force restart, nothing, same issue. Then, true tone disappeared as on option. Finally the proximity sensor doesn't turn my screen off while I'm on the phone etc.

To recap... phone is up and running, but the Face ID won't work, Auto-Brightness is "on" but doesn't work, True tone option disappeared, and the proximity sensor doesn't dim my screen. There's been no repairs done (all original), no water damage, no "hard falls," etc. I've "reset all settings" but did nothing. Haven't done a complete restore yet, but is it even worth it? Is my phone about to die? :-( Is it worth a potential hardware repair? And what exactly should be repaired?