If this is a per-site issue then maybe just use the devtools to profile what's happening. If it's a whole-browser issue then use the firefox profiler and confi

If this is a per-site issue then maybe just use the devtools to profile what's happening. If it's a whole-browser issue then use the firefox profiler and configure it to profile from startup: https://profiler.firefox.com/docs/#/./guide-startup-shutdown https://profiler.firefox.com/docs/#/./guide-startup-shutdown Maybe something obvious pops out.