ipod shuts off when unplugged

would restore (have reset and put into disk mode and didnt help)but ipod cuts off when unplugged from car charger even tho it says its fully charged. When I plug into computer like the updater/restorer tells me to. It doesnt recognize my ipod. Ipod doesnt bring up "do not disconect" message either. After a min or so the ipod will blink from the black screen with an apple in the middle to the screen with the sick ipod message with the ! and the apple support web site beneath it and then back to just a black screen.