I’ve had this wakeup issue with my desktop computer. It used to independently start at odd hours. I tried finding a reason for this behaviour, but it didn’t seem to be that common issue last year or so. There is nothing to wake it up.
I reinstalled Windows, but that didn’t stop the behaviour. It seemed to start after a Windows Update maybe something like a year ago, but which one it was, no idea.
Currently I have my desktop computer switched off from the mains with a separate switch. But I thought that I’d give it another try and the PC started by itself again on Sunday evening. Why? No idea.
This behaviour seems to affect just some PCs. I am curious about the causes for it. But from my experience it seems that Windows is the main culprit and something in the PC setup or hardware/software the lesser one.