Hello,

Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

Let me know if this helps or you need other assistance with the issue.

rmynatt said

Restart Previous Sessions under Startup is NOT CHECKED, but previous sessions load upon startup.

Here are two possible reasons for that:

(1) Crash Recovery

If Firefox doesn't shut down normally, it will detect that and do an automatic crash recovery to the last known point. To avoid this, allow at least 15 seconds between using "Exit" in Firefox and shutting down Windows. By Exit I mean either:

• "3-bar" menu button > Exit
• (menu bar) File > Exit

(2) Windows 10 session resumption

Firefox integrates with the recent Windows 10 feature of restoring open programs when restarting. To turn off the integration, see: Firefox starts automatically when I restart Windows.