I didn't have notification and missed your question.
It's MSI tomahawk x570 with latest bios.
I answered in this topic because during research about my problem I've send here by Google :)
I disassembled pc 3 times
I did about 24 hours of...
I'm fighting this for 2 weeks
Google 5900x random reboots
I checked 3 psus (850W)
Tried newest bios and older one.
Tested memory for about 24 hours in memtest
Checked settings like
Xmp on xmp off - reboots
Full bios stock settings- reboots...
I have 5900x
A lot of stability problems. Try to google 5900x reboots
Im stsrting to loose my mind with this. First uograde after 9 years
From i5 2500k to ryzen 5900x
Can use my computer and been thinking about returning CPU and buying 10850...