Go into Diagnostic Menu by holding the center button and the menu button until the screen goes black, then hold down the center button and the back button. You should get to the diagnostic menu where you can run the internal tests. This should give you the opportunity to find out what is going on with the ipod Here is a video explaining it to you. MY first gut reaction is to say that it probably is your battery....Let us know what your diagnostics tell you. Of course, also try what Richdave is suggesting since it gives you a chance to see if you can access the ipod from your computer. Good Luck

Try forcing the iPod into Disk Mode

If that is not possible then you probably have a hardware fault.