I see you've been reporting this problem for a while: * https://support.mozilla.org/questions/1467799 - version 131 * https://support.mozilla.org/questions/1446108 - version 125 * https://support.mozilla.org/questions/1442287 - version 123 * https://support.mozilla.org/questions/1436689 - version 121 Browser extensions are a logical thing to investigate, especially if you have any less commonly used ones. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either: * Command+Shift+a (Windows: Ctrl+Shift+a) * "3-bar" menu button (or Tools menu) > Add-ons * type or paste '''about:addons''' in the address bar and press Enter/Return In the left column of the Add-ons page, click Extensions. On the right side, find the "Manage Your Extensions" heading. ''If there is at least one extension before the next heading -- "Recommended Extensions" -- please continue:'' Then cast a critical eye over the list below that heading. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything you don't mind turning off for 8 hours? Give it a try with those extensions disabled. Any improvement? ---- Troubleshooting Mode also disables hardware acceleration of graphics. If you want to give that a test in regular mode -- it still requires a restart -- see: [[Firefox's performance settings]].