Hello guys,
I had similar problem with my brand new S21. It restarted once or twice a day and it took a lot of effort to solve this problem. I would like to tell you my procedure at samsung service. First service was total failure, service accepted the phone, but due to GDPR they had to do factory reset. Without my data the didn't find enything and sent me phone back. Second attempted was with full description of my phone problem and list of all apps and settings I made plus all screenshots of all error messages from the members app. Again, they found nothing. The last attempt was with the debug crash report (to enable dial *#9900# and set debug level high, after restart the report is shown on your screen, take photo of all pages using another phone). i insisted on immediate diagnostics, where they found crash report corresponding with the photos I provided. I also logged off from all accounts and deleted all explicit files from the phone, then i turned off phone lock, so they can osberve my phone with my data. And this led to motherboard echange and solving of my phone problem.
