It’s really annoying, isn’t it? All off a sudden your PC wakes up just because some scheduled task is running of some hardware woke up your PC for no reason at all.

The first part to solve this problem is to identify the problem which can be a bit hard.
The following commands can be of help.
You should execute them in Powershell, and start it as Admin.
Command 1:
Get-ScheduledTask | where {$_.settings.waketorun}
And the other commando that follows will tell you what woke the PC last time it did wake up.
Command 2:
powercfg -lastwake
Command 3:
powercfg -waketimers
And also, run “Edit power plan” from the start menu.
Click on “Change advance power settings”.
Here under “Sleep” you’ll be able to disable wake timers.