Gee, after I downloaded the newest version of Firefox, the darn Freezing problem came back.
Taken me days to resolve it, ...but finally I have - by simply updating Adobe...
-you must ensure you have the correct Adobe update for your O.S.
Im certain the problem was caused by a Windows Defender Update ,,,
Anyway help is here, CLICK;
Firefox Keeps Slowing Down/Freezing -Windows Help
Plugin Check
ADOBE Flash Player
ALLOW JAVA ON TRUSTED SITES;
Firefox blocks Java as they report its a security risk, but the solution is here;
Activate JAVA for Trusted Sites
Hope my investigations helps.. if it does, consider donating $10 please, we really do need some help.. 
.