So... I'm having the exact same problem. Newly built PC with a 5950x randomly rebooting.
I finished the build 10 days ago, flashed the MSI bios with v14 and it was all working well except for the power supply (Corsair RM850) which had a really annoying whine.
RMA'd the PSU and bought a Seasonic. It arrived two days ago. All good, no noise, great. But after a bit, it booted unexpectedly. I tried to turn off the RAM xmp, update all drives and even update the Bios to v15.
Before updating, on some reboots I've got a white CPU light on the motherboard, but it doesn't always happen.
Even if it gets stable for a short while, after 10 min or something it boots again. Can anyone help me?
Should I try to RMA the 5950x? Is that done directly with AMD? I ordered this from Germany (out of stock here) and it was a nightmare until it arrived. I really don't want to rely on the shop for that.
Are you getting the same errors I was?
WHEA 18
Eventlog 1101
Kernel-Power 41
Eventlog 6008