There likely is some issue with the hard drive and/or software conflicts.
A suitable backup on external self-powered drive (clone) would be one
way to work around this issue; access & see what else may be lacking.
Try start up in Safe boot mode and see if you can get macOS to load.
And note there will be a login window just for the Safe mode startup.
You can use safe mode to help resolve issues that might keep your Mac from
completely starting up, or to isolate other issues related to your startup disk.
https://support.apple.com/en-us/HT201262
IF the safe mode doesn't work to start the Mac there may be something else
to try & do and see if you can get past this. {An external full system clone on
capable fast rotational hard drive or solid-state-drive (& higher speed cable)
would be one way, if you happen to be ready for eventual hard drive failure.}
So if you have several external or peripheral devices attached via USB or other
wires, unplug all but essentials; external keyboard mouse (display) & maybe too
remove any powered USB hubs during the safe boot test startup. Those could
be a cause of hang up on startup. Their hardware could be detrimental to Mac.
Network connections by wire may also slow the Mac; if it starts looking for boot
drive online instead of local hard drive.