Choose Sleep from the Start menu. If the PC wakes on its own, run powercfg /lastwake before putting it to sleep again. Check active timers with powercfg /waketimers. If the PC never actually enters sleep, use powercfg /requests instead.
01Reproduce the wake on demand
Section linkSave your work, then choose Start → Power → Sleep. Leave the mouse, keyboard and lid untouched. Note the time if the display comes back on. Open Terminal as administrator and run powercfg /lastwake. The command reports the most recent wake, so run it before another sleep test. If Windows reports no useful source, keep the time and move to the checks below.
02Test a device or timer before changing settings
Section linkRun powercfg /devicequery wake_armed to list devices allowed to wake the PC. Being on that list does not prove a device caused the wake. If a USB mouse or receiver is a suspect, disconnect it and repeat the same sleep test, keeping the power button available. Run powercfg /waketimers to list active timers. Compare any named task and time with the wake you observed. If the timer belongs to a known app, check its scheduling options before changing system settings.
03Check whether the PC actually went to sleep
Section linkIf the screen went dark but the PC never seemed to sleep, run powercfg /requests to look for an app or driver holding it awake. Pause a known activity, such as a download you control, and try Sleep again. Run powercfg /a to see the available sleep states. If Standby (S0 Low Power Idle) is listed, the machine uses Modern Standby. Background activity with the display off does not necessarily mean it returned to the desktop.
04When the wake source stays unclear
Section linkKeep a record of the time, whether the PC was plugged in, and the command results. On a work PC, share those with IT. Otherwise, check the PC maker’s support for your model. If you need to put a laptop away before the issue is resolved, save your work and use Hibernate if available, or shut it down.