Please consider turning on send info to Mozilla before posting a question. This helps us help you. As you would not had to type your Extensions and Plugins. Then Tools --> Options --> Performance and untick everything. change the recommended size lower then see how it runs. Hardware Acceleration might have also been a issue so teat with out and then run it and see. Turn other things back on and test it. and repeat. Firefox needs to be restarted after these changes please. Can also try : Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there? https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding Please let us know if this solved your issue or if need further assistance.

None of the suggestions worked. Even scrolling down to the "Performance" settings has a lag and delay. For your information, my Firefox Health Report quit working many versions ago. Thank you.