Did this happen after any kind of update or installation or just out of the blue?
If the former, then you may need to try uninstalling the update to get this resolved. If the latter, then try this and see if it will let you in.
How to enter "Safe Mode" when booting the computer.
In Windows 8 and 10 ...
As your computer restarts, press F8 (possibly a few times) to enter "Safe Mode"
a. Press the "F4" key to Enable "Safe Mode".
(The computer will then start in "Safe Mode" with a minimal set of drivers and services.)
b. Press the "F5" key to Enable "Safe Mode" with Networking.
( Once "Safe Mode" with Networking starts, Windows is in Safe Mode, with additional network and services for accessing the Internet and other computers on your...