Are you on the Insider Program and getting updates recently? If you are not in the Insider program, try the next step below.
Have you tried a soft reset? Hold power and down volume buttons down at the same time for about 15 seconds and release both and allow the boot to start up. See if that helps.
If you are in the Insider program, you can either try a hard reset or use the Windows Device Recovery tool and re flash your software or do the hard reset route. The re flash will load the most recent OS available for your phone and would work better. The hard reset only uses the software already resident on the phone and reloads it.
If you are not already a member of this site, please join so you can reply to posted suggestions and provide more info.
I would back up my data in either case so you don't loose everything.
I'm sure some of the Moderators will reply with answers as well so you might wait for more postings to see if an easier solution would be available.