Helo there colombelli,
I recommend that first you reset the iPod shuffle. Here is an article about doing that named Resetting iPod shuffle found here http://support.apple.com/kb/HT1655.
To reset iPod shuffle:
- Disconnect iPod shuffle from the computer (if connected).
- Move the switch on the iPod shuffle to the OFF position. Note that when iPod shuffle is off, the green stripe by the switch is not visible.
- Wait five seconds. For iPod shuffle (3rd and 4th generation), wait ten seconds.
- Move the switch to the play in order or the shuffle position. The green stripe will be visible in either position. For iPod shuffle (2nd and 4th generation), slide the power switch on (and you can see the green stripe).
If that doesnt get the iPod working correctly, then the next step would be to restore the iPod. Here is the article for that named Restoring iPod shuffle to factory settings found here: http://support.apple.com/kb/HT1481.