Firefox 'solves' this by only loading tabs that have been given the focus upon auto-restart. So, if you have 10 tabs opened, and your computer restarts and Firefox is opened, the only tab that will actually load is the one that was last active.
I don't like this. It just feels like Firefox is being lazy to me. I notice I have to wait a second or two when I switch to another tab. This is annoying because I remember seeing the page load before I restarted. My subconscious doesn't realize that it was a different process. I'd rather my browser and everything else involved work a little harder to give me the illusion that nothing has changed after I restart.
To always load all tabs after (re)start, go to Preferences > Tabs and uncheck "Don't load tabs until selected". ("Preferences" may be called Options or something on Windows or Linux, I can't recall right now.)
I would argue this is a sane default setting (it trades some waiting time when switching to a different tab for snappier start-up). Regardless, Firefox gives you the option to choose your behavior, which I would argue is the non-lazy thing to do (however simple).
† Note I am on Nightly, so it's possible this preference is not yet visible in the release version. It probably is, but just to be clear.