Mac log on screen is all i can see?

Try booting into Safe Mode according to How to use safe mode on your Mac . If you can then reboot normally and see if the problem persists.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

Actually just the boot into safe mode is enough as this is what it does:

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

If booting back into normal mod isn't corrected then it's sorting else causing the problem.