Take a look at about:performance page, maybe some background tab is too active? Try some tab suspend extension like https://addons.mozilla.org/en-US/firefox/ad

Take a look at about:performance page, maybe some background tab is too active? Try some tab suspend extension like https://addons.mozilla.org/en-US/firefox/addon/auto-tab-discard/ https://addons.mozilla.org/en-US/firefox/addon/auto-tab-disc...