That shouldn't obviously be happening if that's not how your phone is set up to work.
That isn't happening on my partners or daughters s20.
First please put the phone in Safe Mode which disables your downloaded app's but let's your stock app's keep working. If the issues stop then this highlights a downloaded app as the possible issue. Come out of Safe Mode and start deleting your most recent downloaded app's one at a time until it stops @Anonymous User
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.
I agree with @BandOfBrothers, this should not be happening.
No consolation to you but it does not happen on my Galaxy S20 Ultra 5G on Android 11 unbranded firmware for the U.K. particularly as you have not enabled... Settings > General management > Reset >Auto restart at set times.
I think running it in Safe Mode will determine if some 3rd party app or setting is causing your issue. Perhaps a cache partition wipe may be called for.
Having the same issue since the last update, appears to be literally every time overnight when its not used, all auto restarts are disabled and also i believe only started since the last android update
Nope. It is still happening to s20 phones in March 2021. My phone has been restarting mostly during the night when I have been sleeping but it has restarted in my hand before randomly. I have tried everything. I have factory reset the phone, cleared the cache, removed third party apps, turned off auto restart, and put the phone in safe mode and it still restarted overnight. So frustrating, so many threads about this and Samsung is doing nothing.