How do I get back the window with all my tabs?

Recently, my Firefox was acting up and wouldn't respond at all. Therefore, I closed it down and started it back up again. It was working fine, and all of the tabs were where they were suppose to be. But the Firefox was slowing down and was acting up again. Therefore, I closed it down and then restarted the computer.

When I went to get back on Firefox, my window was gone and I couldn't it, nor any of my tabs. This hasn't happened before. Firefox has crashed many times and despite how annoying it is, my tabs always seemed to come back. But now, they're gone. Any help you could give would be very helpful. I really do not want to go back and look for my tabs in history, since I won't be able to find them all.