Is it still charging if you use the adapter? If yes, let it charge for 15min, then connect in recovery mode.

If still having problems then I would restore from backup via iTunes. If still problems restore to factory defaults/new iPod also via iTunes.

If it will not reset (pressing and holding the Home and Power buttons until it restarts) and has been charging over night, it's a hardware issue. You will need to take it in for service.