[burnte]

My custom-build desktop had an issue with the previous AM4 motherboard I had where if you told Windows to hibernate, the entire machine would shut down as normal, but then a few seconds later it'd wake back up by itself and unhibernate. I had to turn off the PSU power switch during those few moments to keep it in hibernate mode. New mobo and that's gone now. BIOS updates never helped. Really odd.

[iamtedd]

Probably no help to you now, but if someone has a Windows machine that keeps waking up by itself, you can see what triggered the wake by running

    powercfg /lastwake

in a command window as admin.

[burnte]

True, and that helps if it won't go to sleep. This was some weird bug in either the board or the bios.