Hi, Please go to ur settings and go to battery and device care and click on the 3 dots on the right hand side and check if u have set the automation on. Please also check the auto restart at set times. If these are on please turn them off as this is the reason. If they are off then ur phone is faulty needs to be replaced.
My s21+ has done it since the day I got in, when it was first released. Restarts about 20 times a day, but only does it when a system update is installed and then it restarts about 20 times a day for about a week and then fixes itself. Factory reset doesn't fix it. Sometimes says that some apps are overloading the CPU.
We have this problem. Sansung will not replace the phone. Already been sent to them once and they updated the firmware. Didnt work. Now worse then ever. Have a doorstep repair booked for this week. Done multiple factory resets and the auto restart function is off
It is now fixed. When sent to samsung by post they sent it back with no actual repair. I arranged a further door step repair and the nice man changed the motherboard. 7 days now. Phone works better than new