PC wakes up from sleep mode almost instantly

1. Check the Wake Up Timer
Open Device Manager, expand System Devices, and locate Wake Up Timer.
Right-click Wake on Timer, select Properties > Power Management, and uncheck “Allow this device to wake the computer”.
2. Disable Wake on Network
In Device Manager, expand Network Adapters, right-click the network card, select Properties > Power Management, and uncheck “Allow this device to wake up the computer”.
3. Check the Task Scheduler
Open Task Scheduler and check if any tasks are set to wake up the computer.
Right-click the relevant task, select Properties > Conditions, and uncheck “Wake the computer to run this task”.
4. Update or Rollback Drivers
Open Device Manager and check if there are any devices with yellow exclamation marks.
Update or reinstall the driver (give priority to the official website driver).
If the problem occurs after updating the driver, try to roll back to the previous version.
5. Check the power settings
Open Control Panel > Power Options > Change Program Settings > Change Advanced Power Settings, find Sleep > Allow Wake Timer and set it to Disable.