My PC did have the reboot option in the settings selected. Now I removed it, so I see the blue screen.
But I have the minidumps, that windows generates.
This also means that it IS windows who restarted my PC !
Good news I think:)
I remeber that I once used some tool to analyze the minidump files. They should have the same info as the bluescreen, and more.
I have to goole for the tools now

I run a CPU test for 10 minutes. It did not find an error, but did write at one point:
"spurious 8259A interupt IRQ7"
I dont know what spurious means, but I will google that also

I have two case fans. One in front blowing air in, and one in the back, blowing it out.
The case temp is now after some test running and now finlay back in windows at 40c, it is the alarm I set at 50c, but it never kicks in.