Yes probably so. Before you do, when you first connect to iTunes you should take a good look at the bottom bar that shows how much space is taken by photos, apps, music etc. - so at least you have a greater understanding of what has caused you to run out of space.
Check the info page in iTunes. If you have an unusually large amount (more than a couple GB) in the Other section, you'll want to restore. This is where the OS and a few other things, such as email, settings and SMS, are stored. If it has a more than a couple GB, there are probably some corrupt video files there taking up space.