it could be a few things however yustr might be on the right track... try plugging it into the wall outlet and let it charge. once it has enough juice you may want to try a soft reset on the ipod...
To reset your iPod (5th generation):
1. Toggle the Hold switch on and off. (Slide it to Hold, then turn it off again.)
2. Press and hold the Menu and Select buttons until the Apple logo appears, about 6 to 10 seconds. You may need to repeat this step.
* Tip: If you are having difficulty resetting your iPod, set it on a flat surface. Make sure the finger pressing the Select button is not touching any part of the click wheel. Also make sure that you are pressing the Menu button toward the outside of the click wheel, and not near the center.
* If the above steps did not work, try connecting iPod to a power adapter and plug the power adapter into an electrical outlet, or connect iPod to your computer. Make sure the computer is turned on and isn't set to go to sleep.
http://www.apple.com/support/ipod/five_rs/
then try plugging it back into the computer.
check out that apple support site they walk you through everything...
reset, retry, restart, reinstall, restore... good luck