Your iPod’s Hold Switch
Your iPod has a Hold switch on the top, near the headphones jack. The hold switch locks the iPod buttons, this preventing the volume from changing (and bursting your eardrums) if you accidentally brush against the scroll wheel, or preventing the iPod from turning itself on in your pocket or backpack if something brushes against the power button.
If your iPod refuses to turn on, check the position of the Hold switch. Slide the Hold switch away from the headphone connection, hiding the orange layer, to unlock the buttons. (If you see the orange layer underneath one end of the Hold switch, the switch is still in the locked position.)