Now maybe ive just never noticed this before, but when I turn on my xbox and just let it sit on the interface screen eventually the whole screen goes dim. Now is it just going to sleep or some kind of power saver that is supposed to kick in when the system is idle, or what? Cuz when I move or press a button on the controller it brightens back up.

It is kind of like a screen saver. So that you TV doesn't burn out when you leave it on like that. There is nothing wrong with your XBox, it's completely normal