To be more clear: Yes, I have set my options to "show windows and tabs from last time". No, I did not check "clear memory on shut down" or "start private session"

Also, it saves my tabs when I restart the browser, but when I shut down my computer and start up again, Firefox does not show my tabs from last time. The same thing happens with sites I've logged onto before; it logs me out after I shut down my computer.