At least for me after FF updates itself it won't let you open a new tab or anything until it restarts. According to this Reddit post this is due to it being updated by the package manger so maybe it's a Linux only issue?: https://old.reddit.com/r/firefox/comments/jwx54y/firefox_for...
It's due to the "unattended upgrades" feature. You can blacklist FF from getting those upgrades with a change to /etc/apt/apt.conf.d/50unattended-upgrades. Add "firefox" to the "Unattended-Upgrade::Package-Blacklist" section. I find manually upgrading much less annoying than having my browser randomly lock up on me.
