iPod classic 160gb showing NO music or any files at all
It sounds like your database is corrupted. This has happened to me twice and I did this to fix it both times:


Plug your Ipod into your pc / mac 
Find the Ipod in Windows Explorer / Finder 
"Unhide" Hidden files &amp; Folders in Windows (if you have Mac follow these instructions: http://www.macworld.co.uk/how-to/mac-software/how-show-hidden-files-in-mac-os-x-finder-3520878/)
Go to: iPod_Controls > iTunes (the hidden folders). 
Locate "itunesDB" and rename it: "itunesDB.old" (this is the newly corrupted database).
Locate "itunesDB.old_mlpmp" and rename it: "itunesDB" (no file extension). This will restore the automatic backup of your database.


If you added music since your last sync, you'll probably have to add the music again, but this is way better than restoring and syncing your entire library.