Assumming that the battery has some charge left in it, try a reset.
To reset the iPod, turn the lock switch on, then off again and then press-and-hold both the Menu and Select (centre) buttons down together for at least ten seconds. Does the iPod restart?
Alternatively, if you didn't put the iPod on charge, and the battery has run down, you need to leave the iPod on charge for at least thirty minutes before you see any sings of life from it. Let it fully charge.