Since a week or 2 Firefox has been loading web pages very slow. Or it does load them but it takes a good 3 seconds before i can scroll or enter anything.
This morning also it froze up for a good 10 seconds and then it loaded the web pages again. Especially when i am browsing on a forum and return to main page or something. It just takes ages before i can select anything. It loads somewhat slower also but the part of it that i cannot select anything or scroll down before it stops thinking.
Try to start Firefox in Safe Mode to see if there is an add-on that is causing the slowdowns. https://support.mozilla.org/en-US/kb/Safe%20Mode
A possible cause is a problem with the file places.sqlite that stores the bookmarks and the history.
You can also try to repair the places database with this extension:
A possible cause is security software (firewall) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.
Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.