I've bought an iPhone 12 Mini 4 days ago and since then it has been restarting every day. Now it's something like 5-6 restarts in total. I went to Settings -> Privacy -> Analytics & Improvements -> Analytics Data to see if I could find any bug reports there and I found 5 panic-full reports. They all had the same socld: "0x00008101".
iPhone 12 Mini restarts every day all by itself
UPD I fixed my own problem. As it turned out the SIM slot has some structural features in some iphone 11 and iphone 12 models resulting in such sudden restarts. I took out my SIM card and just put it back. It's been 2 weeks now without any issues.