Boot into Safe Mode
Start up your Mac in safe mode - Apple Support
After booting into Safe Mode, try a normal reboot to see if it is fixed. If this does not work, reset the SMC if your Mac supports it:
How to reset the SMC of your Mac - Apple Support
If this does not fix it, reset NVRAM (if your Mac supports it):
Mac startup key combinations - Apple Support
Then reboot normally to see if it cured the problem.
If not, boot into Recovery.
Mac startup key combinations - Apple Support
Run Disk Utility from there to perform First Aid and repair the disk's file system.
Restart, see if the problem is gone. If not, reinstall the MacOS. Do not choose an option to format or erase the disk, choose the option reinstall the MacOS. This will not affect your files.
How to reinstall macOS - Apple Support