Might start with checking the boot log to see if something failed.
Should end with "Starting Authorization Manager..."
If it stops at another point we may be able to help you determine what happened.
I ran across an issue where my home server was running a fsck across a 4TB volume on every reboot but not on cold boots, this resolved itself after an update.
If you reboot the system when the loading 'f' shows up pressing alt+d (I think) will display the verbose output hidden behind the splash screen.
Hope this helps you troubleshoot the issue.