Help!!! iPod won’t play unless plugged in ?? 10 pts?

its an ipod 4g ( http://reviews.cnet.com/mp3-players/apple-ipod-nano-fourth/4505-6490_7-33247196.html ) and it will not work unless it is plugged into the computer through the usb. When I unplug it, the screen goes blank and will not turn on again. I have tried restoring it a couple times to see if that fixes it and it still has the problem. your help is greatly appreciated