When your iPod Classic stops responding, try to shut it off normally and restart it. If the device won't respond at all, force a reboot to clear up the problem and get back to your music.
First things first: try turning off your iPod normally by pressing and holding the Play/Pause button for several seconds. If the screen turns off, but then lights up again when you remove your finger, the iPod hasn't turned off. Try setting down the device and using your nail to press the button, since any motion prevents the command from working. If the iPod does shut down properly, wait a few seconds, and then press any button to turn it on again.
When a normal shutdown doesn't work, use this method to reboot:
Flip the Hold switch on (colored orange) and off.
Press and hold both Menu (at the top of the wheel) and Select (the center button) for about 10 seconds until the the iPod reboots, displaying the Apple logo.
Unfreeze After Syncing
When you sync your iPod with iTunes, the screen wisely displays "Do Not Disconnect," because removing the cable during a sync can cause lost data. However, sometimes the iPod doesn't stop showing this screen even after you click Eject in iTunes. If the screen doesn't change after several seconds, unplug the cable anyway. Usually, the iPod will resume normal function without requiring a reboot.