When booted in SafeBoot (shift key held on startup)
you could try Disk Utility 'repair disk permissions' to see
if it helps, then restart after. And if not try something else...
You could try & reset the 'Power Management Unit' (PMU)
refer to your computer model in article
if that fails to do anything after trying it a few times...
Try a reset of the PRAM:
- Shut down your Mac.
- Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
- You will need to hold these keys down simultaneously in step 4.
- Turn on the computer.
- Press and hold the Command-Option-P-R keys before the gray screen appears.
- Hold the keys down until the computer restarts and you hear the startup sound for the second time.
- Release the keys.
After resetting NVRAM or PRAM, you may need to reconfigure your settings for
speaker volume, screen resolution, startup disk selection, & time zone information.
Hopefully one of these helps.
Good luck & happy computing!