As Lexpex suggested
Start up your Mac in single-user mode or verbose mode - Apple Support
and use recovery
you may also try the following steps in order
Shut down
Disconnect all external devices
Mac Mini: all but video, mouse, keyboard
iMac: all but OEM mouse, keyboard
Laptop: all devices
reset the SMC, repeat two or three times
https://support.apple.com/en-us/HT201295
reset the NVRAM
How to reset NVRAM on your Mac - Apple Support
then boot into safe mode
https://support.apple.com/en-us/HT201262
then reboot normally with devices disconnected.