Likely this is a hardware issue but would like some suggestions. Two days ago, got this 7 years old PC, very fast. Wiped out Win 8 and installed 3 different pups, frugal install to internal SSD. Now I am noticing poweroff (wmpoweroff), even Ctrl-Alt-Backspace followed by poweroff, result in rebooting in all pups. Reverting to default bios setting, replacing CMOS battery, removing and inserting 1/2 RAM sticks all result in same rebooting behavior when I shutdown. Only way to shutoff is by >3sec power button press. Anyone know a fix?
If I boot into a usb with Ventoy, I am able to shutdown normally as long as I don't install to internal HD!. When I installed ubuntu into internal SSD and boot from it, same cycling boot behavior returns. I am beginning to think maybe it is the motherboard?