If your iPod 4 freezes and you need to restart it, follow these steps:

  • Hold down Hold and Home button at the same time.
  • Continue holding the Hold and Home buttons after the slider to turn off the iPod appears.
  • Let go when the screen turns black.
  • Wait for about two minutes
  • Hold Home and Hold button to turn iPod back on

If you need to reset your iPod to factory settings:

  • Choose Settings>General>Reset>Erase All Content and Settings.
  • Connect iPod to computer .
  • Opt to restore to New Device.

Resource: About iPod