generally if the iPod is completely drained (this was the case on both my 4Gs and my 5G) when you try to start it up, the battery comes up on the screen with the triangle/exclamation point on top of it for 3 or 4 seconds and then goes away. It's the iPods way of telling you that it's not starting because it has no battery. I don't know why you haven't seen it before. hmmmm...no i'm confused. I know it does, because mine is doing it right now...damn ipod battery.
-JE
-JE