An obvious question - have you unlocked the iPod?
If you can't unlock it, iTunes doesn't recognise it and it will not reset (rather than reboot), then there are two options.
1. Try resetting it. Even though it appears to stay locked, move the lock switch to the _lock position, then back to unlock_ and then press-and-hold the
Menu and the
Select (centre) buttons together for ten seconds. The Apple logo should appear and then the iPod will start up again. Try this three or four times - if it part resets, then leave it and it will probably sort itself out after a few minutes.
2. If the above advice doesn't work, then simply leave the iPod until the battery runs down. If the display stays on, then the battery
will run down after a while, perhaps 24 hours. If the display has turned off, then try starting the iPod normally. If that doesn't work, try the reset procedure again. Finally, if the display has turned off but the iPod still won't respond, try plugging it into iTunes to see if iTunes responds.
One thing to note; if you are waiting for the battery to run down, make sure you leave enough time for this to happen because if you don't, adding more power to an iPod that is locked up will make sure it stays locked up.
Phil