Same issue with so many m series phone even I am facing same issue from the last update and all service center have same answer problem with motherboard still I suggest please visit nearest service center
Have u checked this by any chance this is on. Under setting search auto restart. If it is off then just check any latest new app been installed on your phone. Also try to start your phone in safe mode just incase if this problem comes then just ask samsung to replace the phone if it is under warranty if not then ahh one feels really sad spending money on what restart. Irritating. Well in my m51 it happens every now and then but still it is working I keep taking my backups every now and then one does not know. This is for sure no more samsun M series only A series. They have a good command on them. This I have seen. More over samsung phones are only good for 3 to 4 years max. After that upgrade them as the Co. Stops giving you any update on them. Infact it takes it away from you. Which just happened on my Samsung a7 2017
We would request you to register your concern in Samsung Members Application. So, that our concern team gets back to you as soon as possible.
Please follow this path to register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
Note. please attach the error log file within 15 minutes of the error occurred.
