I haven’t experienced this, but it could be a problem relating to your default Firefox profile.
You could try launching a different Firefox profile using the terminal:
firefox --profile ~/.mozilla/firefox/profile.default-esr
(change profile.default-esr to one of your non-default profiles)
Or you could move everything from the firefox folder to a safe location somewhere else and then try to launch Firefox:
mkdir -p ~/ff/ && mv ~/.mozilla/firefox/* ~/ff/ && firefox
While I haven’t experienced your issue, I have experienced a different bug that I mentioned in this comment on another post:
I really hope that the Firefox developers can fix these bugs soon.