Same problem as so many people: My computer wakes itself, but I can't determine the source. Windows 10. It's happened around 3:40am, 12:21am, etc. Seems to happen every few weeks.
These are some details regarding my system configuration after the wake happens:
powercfg -devicequery wake_armed → NONE
powercfg -waketimers → There are no active wake timers in the system.
Power Options Advanced Settings → Sleep → Allow wake timers → Disable
(Classic) Control Panel / System and Security / Security and Maintenance / Automatic Maintenance → "Allow scheduled maintenance to wake up my computer at the scheduled time" unchecked.
All wake on "Magic Packet" or "Pattern Match" or "Link Settings" of all network adapters are set to "Disabled" in the Advanced settings of the devices in Device Manager.
ASRock Z170 Extreme 7+ motherboard (no "wake from sleep" options found in UEFI).
Event Viewer → Wake Source: Unknown
powercfg -lastwake → Wake History Count - 1, Wake History : Wake Source Count - 0