I have gone through 2 motherboards trying to hunt down this issue. When I try and boot from USB either unraid or Fedora a few seconds in my computer hard resets.
Here are my specs.
SAMSUNG 970 EVO Plus SSD 2TB - M.2 NVMe
MSI B550-A PRO ProSeries Motherboard
Corsair Vengeance LPX 64GB (2x32GB) DDR4 3600(PC4-28800) C181.35V Desktop Memory - Black
4 X Seagate 6 TB 3.5" Internal Hard Drive ST6000NM0044
AMD Ryzen 9 3900X 12-core, 24-thread
Here is an image I was able to capture.
Do I have a bad CPU?
I not familiar with Unraid OS or that much about Linux OS.
Try just for troubleshooting purposes only, disable half of your CPU processors and see if the problem occurs. Just in case there is some incompatibility issue with running all 12 cores on the CPU.
Also try with just one 32GB RAM Stick to see if it is a RAM incompatibility issue with 2 sticks installed.
Also you are using 64GB of RAM Memory, Is your RAM Part number listed under MSI Support QVL List for the 3000 series processors for your motherboard: https://www.msi.com/Motherboard/support/B550-A-PRO#support-mem-19
Looking at your MSI QVL List for the 3000 series processor there is only one Corsair rated at 3600Mhz listed:
But since your computer is booting up and working normally most likely the RAM you have installed is compatible.
As to your Processor I suggest you open a AMD Service Request under Warranty and see if they believe you need to RMA the processor to be checked: https://www.amd.com/en/support/contact-email-form
EDIT: Do you have the latest BIOS installed. At MSI Support is shows one from 09/27/2021 as the latest. Also see if you have the latest AMD CHIPSET drivers installed from AMD download page: https://www.amd.com/en/support/chipsets/amd-socket-am4/b550