If your Mac sleeps or wakes unexpectedly
If your Mac doesn’t go to sleep when you expect it to or if it wakes up unexpectedly, you may need to change your sleep settings. If that doesn’t work, something may be waking your Mac.
Check your system’s sleep settings
Make sure the sleep settings are set the way you want.
On your Mac, choose Apple menu
in the sidebar. (You may need to scroll down.)To set the amount of time that should pass before your computer goes to sleep, do one of the following:
Click the Turn display off on battery when inactive pop-up menu on the right, then choose an option.
Click the Turn display off on power adapter when inactive pop-up menu on the right, then choose an option.
You can also turn off “Prevent automatic sleeping on power adapter when the display is off” in Battery settings.
Check your system’s network access setting
Other users may be waking your Mac remotely to use its shared resources. If you don’t want this to happen, choose Apple menu 
If you’re using a Mac laptop: Click Battery
in the sidebar (you may need to scroll down), then click Options on the right. Click the pop-up menu next to Wake for network access, then choose Never.If you’re using a Mac desktop computer: Click Energy Saver
in the sidebar (you may need to scroll down), then turn off Wake for network access on the right.
Check your system’s sharing settings
People using shared services on your Mac can prevent it from sleeping. For example, they may be using a printer connected to your Mac or accessing shared files stored on it. If you don’t want this to happen, you can turn off any services you don’t need to use.
On your Mac, choose Apple menu
in the sidebar, then click Sharing 
on the right. (You may need to scroll down.)Turn off the service you don’t need to use.
Check your system’s activity
Processes running in the background can prevent your Mac from sleeping. Check Activity Monitor to see if a process is unexpectedly using your Mac computer’s central processing unit (CPU).
Open a Finder window, then go to Applications > Utilities > Activity Monitor.
Click the CPU button at the top.
Check the software or SMC
Update macOS: Certain software issues can be resolved by keeping your software up to date. See the Apple Support article Update macOS on Mac.
Use safe mode: Safe mode can help you to determine whether an issue is caused by software that loads as your Mac starts up. See the Apple Support article Use safe mode on your Mac.
Reset the SMC: Resetting the system management controller (SMC) can resolve certain issues related to power. If you have a Mac with Apple silicon, just restart your computer. For other Mac computers, see the Apple Support article Reset the SMC of your Mac.
Check to see if something else is waking your Mac
Check any of the following:
Unexpected keyboard presses or mouse and trackpad clicks: Key presses and mouse or trackpad clicks can wake your Mac. If your Mac wakes when you’re not present, something may be pressing the trackpad or mouse button or keyboard keys.
Apps: Apps that access a disk can keep your Mac from going to sleep. For example, Music accesses your disk to read the songs it plays, and DVD Player accesses the optical disc drive to play films.
Spotlight indexing: If Spotlight is indexing your hard disk, your Mac won’t go to sleep. Open Spotlight
to see if it’s indexing. Indexing can take several hours, depending on the number of files on your Mac.Connected storage and devices: Malfunctioning USB and Thunderbolt storage and devices may keep your Mac from going to sleep. Disconnect those devices and see if your Mac goes to sleep. If it does, reconnect each item, one at a time, until you find the one that’s malfunctioning. Contact that device’s manufacturer for more information.