Holding down the center/select button and the menu button will reboot your ipod. See if that helps. Also, I'd recommend something else- I had nothing but trouble with my ipod classic until I spent $20 to get Mac OS Mountain Lion. It did what you said and sometimes wouldnt play, or wouldnt power on...
Try rebooting your ipod and let me know what happens and maybe in the future obtain Mountain Lion to aide your ipod in functionality.