wokemup

This might be a silly suggestion but check to see if you have any miscellaneous usb or other peripherals hooked up to the system. I just recently had a tiny bluetooth usb adapter in a system and it was conflicting with the motherboard bluetooth. I would have thought this was no big deal but it did keep randomly causing reboots until I took our the bluetooth adapter. Which in general to troubleshoot its good to just simplify the system as much as you can and see if the reboots keep happening. I hate these types of problems. I would have suggested PSU as well. But I see you confirmed that was not a problem.

Im going to try my best to help since this community was so helpful for the 80 hours I put into getting my unraid up and running last week. (and now it is so, so, so sweet!) I dont have the exact same MB you have. I have the MSI B560M PRO-VDH WIFI LGA 1200. And I had this problem too. It could be a MSI bios issue. The problem is you simply cant boot up to the unraid GUI interface. So you must let unraid boot up with the first option (that does not mention GUI). This boots in text only mode. Then when its finished you can login to your home IP. For me this is ultimately what unraid will boot with if you let the timer tick down anyway. So now I can reboot it without hooking up a monitor, mouse, keyboard etc. So hope this helps! And thanks to the community for all their help from all of my google/duck duck searches!