Microsoft has a strange idea that anybody would want their PC to be woken up during the night to do the maintenance task. WHY???
All my PCs have encrypted drives and password is required for windows to boot. So even if PC manages to wake itself up – it is stuck on password prompt. DUH!
Way to check it:
If you see
Reason: Windows will execute 'Maintenance Activator' scheduled task that requested waking the computer.
Head to Control Panel -> Security and Maintenance -> Expand Maintenance. There will be an option to disable waking your PC for Maintenance.
And here is another discussion with some answers, though people do report that Windows 10 is notoriously bad for ignoring any/all of these settings and you will still get your PC woken up at night, barring all but unplugging it from the mains
And another discussion with a lot of details.