Try the Hard Reset
- After charging till full charge, at least 2 hours (preferably 4 hours)
- Toggle the Hold switch, make sure you dont see the red mark when you do the next step
- Reset the iPod -> Press Menu and Center button simultaneously for about 10 secs or till the Apple Logo comes ON
- Then release the buttons
- Select your preferred language.
Here is the Apple support Article on the 5Rs
http://www.apple.com/support/ipod/five_rs/classic/
Do the iPod Disk Diagnostic as posted by tt2,
https://discussions.apple.com/thread/3784647?answerId=17776595022#17776595022
If you have high numbers on the first 5 items, better bring back to Apple Store for a replacement.
Good Luck!