I've reinstalled from scratch twice and used two separate machines.
At first I had thought when my computer would suddenly and without warning this was a power issue in my apartment.
But my television and other devices wouldn't restart clean and would need to be turned back on. So it was solely the computer.
Next I was concerned that my computer was broken or overheating. So I purposely ran separate game benchmarks at high settings.
No issues.
So it was Cura, I concluded and decided to test its cause. But that proved impossible. With Slice or Without, With Model or Without, fresh install, or fresh machine.
Nothing changed the inevitable. Anywhere from minute 1 to when I'm saving a slice I've worked on for an hour will always result in a computer brick and safe restart.
Only happens when Cura is in launched but doesn't have to be in use. Proved by leaving in background having forgot I had launched it earlier.