Lindsey:
Oh dear, this was the first sign that my ipod was fecked. Not to worry you, lol. I had the same thing happen a few times and it completely deleted all my songs, etc. Try not to be too annoyed if when you get it working, yours songs aren't there. Luckily mine was still under warranty and i got it sent off and replaced with a brand new one within 2 weeks, if that, so i was chuffed.
If you have the the old ones 1st-3rd gen then you need to hold down menu and the play/pause button for about ten seconds.
If you have the 4th gen (like me) you need to hold down menu and select for, again, ten seconds. When you do this, the apple logo should appear. It does a little reset thing with a scroll bar. Oh and if i remember correctly, it needs to be connected to the charger when you do this... TBH it was all a bit hit and miss with mine trying different combos, but this is the one that worked. Good luck and i hope it's nothing more than a little freeze!
p.s. Try restarting without the charger first. If none of this works, you can get a download from the apple website, it's a freebie, an updater. This will restore your ipod and i'm sure this does actually delete all your songs aswell. Stupid I know. But if it starts to freeze regularly, you might have to look into sending it back to apple. They don't even bother to atempt fixing them, they just replace it if it's under warranty.
Oh and another thing, if it is still under warranty, it will be void if you attempt to fix it yourself or if there are signs of the unit being tampered with.