Photos keeps going into Restore mode

You might have a problem file. Do you use iCloud to synchronize your Photos Libraries on your devices? If so, do you have "Optimize Storage" checked in Photos>Settings>iCloud?

Is your Photos Library kept in the Pictures folder, or are you using an external drive for the Library?

You should try these things:

• Restart the computer (of course)
• Re-start in Safe Mode. This bypasses certain potentially disruptive processes. Safe Mode is different for different computers, so see this: 

     Start up your Mac in safe mode - Apple Support 

• Make a new user and see if the same problem recurs with it
• If you are not using iCloud, then try usiong another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens. You can create a new Library by closing Photos and then option-clicking on the Photos icon.

The idea is to find out if the problem is with the Library, with your account, or with caches and login items, and stuff like that. One of these steps may fix the problem, but their failure to work also helps figure out what's happening.

So let us know, and the results may lead to further things to test....