If you’ve used a computer or other technical device and seen it freeze, you know that restarting it usually fixes the problem. The same goes for an iPod.
All iPod Touches: How to Force Restart (1st, 2nd, 3rd, 4th, 5th, 6th, 7th Generation)
To restart your iPod touch, perform a hard reboot. To hard reboot your iPod, press and hold the Sleep/Wake button and the Home button (the power-off slider appears briefly while you hold the buttons) until you see the Apple logo. This may take at least 10 seconds.
Whether you need to perform a hard restart on an iPod nano depends on the generation of the device.
If the first attempt doesn't work, plug your iPod nano into power and try restarting it.
