If you put your Windows 10 computer in Sleep mode and it's randomly coming awake during the day or in the middle of the night, without a screensaver, then there's a good chance that the issue is with your Monitor(s). If you have an old monitor, then it could be going bad and waking up your computer. If you have a second monitor, then try using just one monitor at a time, to see if the problem persists. If the problem occurs with one monitor, and not the other then you know it's an issue with the faulty monitor.
Make sure you also have proper power settings for your display. Go to: Control Panel > Hardware and Sound > Power Options > Edit Plan Settings.
NOTE: In some instances, a faulty monitor may also slow down your computer start-up time.