Kreuznik

You have a hardware fault somewhere. There should be an option in the Windows Startup Config to stop on BSODs if its not already. This will allow you to catch the error code. Often times the code is for a generic hardware fault, but sometimes it will point to the specific hardware. Take all the hardware out, and start with the basics. Just what you need to POST. Run it until your sure your likely not going to BSOD. Work your way up from there, piece by piece (even installing RAM one by one). Once younger a fault, uninstall the last piece of hardware and test again.

The 3rd Gen Ryzens idle hot. Actually, the temps in general are hot. They're a smaller size and larger power, so they generate more. Even with optimized fans, I idle on my 3600X at about 55.. Gaming runs me ~70. Benchmarks break the 80 mark.. As soon as the load is off though, the temps drop within seconds. Don't worry about it unless your temps are running over 80 consistently.