Whatever the issue, this isn't Session Restore causing it, as it doesn't prompt for any passwords (and you can get the same issue by saving all tabs to bookmarks, restarting Firefox cleanly and then reopening those bookmarks all at once).
This should be better handled in Core:Security UI (or maybe Core:Networking such as the similar bug 356097).
Whatever the issue, this isn't Session Restore causing it, as it doesn't prompt for any passwords (and you can get the same issue by saving all tabs to bookmarks, restarting Firefox cleanly and then reopening those bookmarks all at once).
This should be better handled in Core:Security UI (or maybe Core:Networking such as the similar bug 356097).