After more than 1 month I can say that my Ryzen 1600 is stable now. Unstable idling fixed!
The solution for me was to set the "Power Supply Idle Control" to "Typical Current Idle" in UEFI settings. Apparently that forces the CPU to not enter the lower power states, where it crashed.
Thanks to MekoProgram [NekoProgram Misskey Edition] (npub1lsk…66t9) and all the people who commented!
ohh I didn't know about that setting. It was on "Auto" and I just set it to "Typical Current Idle".
I was wondering if the problem was related to idling, because it doesn't freeze when playing games. So this makes sense.
Unstable idling, like car engines...
Let's see if it works. Thank you so much!