Start off with trying a different USB port and a different cable. Take a look at the dock connector of the iPod and make sure it is clean, you can clean "gently" with a toothpick and/or use some compressed air. Make sure the pins are not bend. Also check on here and see what works for you http://support.apple.com/kb/ts1369 and try to reset your iPod.
To reset your iPod:
- 1. Toggle the Hold switch on and off. (Slide it to Hold, then turn it off again.)
- 2. Press and hold the Menu and Center (Select) buttons simultaneously until the Apple logo appears, about 6 to 10 seconds. You may need to repeat this step.
o 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.
o 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.