First of all, you'd probably want to move this question out of iPod classic category to iPod touch one.
Try reconnecting your cable. Try connecting to your computer instead of wall socket, or vice versa.
Try resetting, restoring, restoring from backup. Make sure there's nothing wrong with your cable and try another one. The problem might be in your connector or the cable, if so — you might want to ask for a repair in your local Apple Store or Apple Authorised Reseller.