If your iPod Shuffle is not functioning properly, you may want to perform a hard reset.
On both the 1st and 2nd generation iPod Shuffle, you can perform a hard reset on it by powering it down for 5 seconds then powering it back on. Also be sure you do not have the device attached to your computer or any other device while doing this. This is the only thing that can be done to reset it.
If the device is still giving you problems, you will want to restore the software using iTunes.
1. Plug the Shuffle into your computer.
2. Select the device in the left pane.
3. Choose Summary.
4. Select Restore.
For more information see Apple’s document on resetting the iPod Shuffle here.