When does this happen? Startup, while surfing . . . . Is it just once or repeated?

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

While surfing, I have a few common pages kept up in tabs like reddit, fb, protonmail. fb is has been in a container, I just put reddit in container. I have a newer Dell laptop which is updated and always keep ff update, also have duckduckgo essential, ublock origin, active reader view, fb container has been on but added also fb container too but after freeze issue, mega,