It has no effect on your Xbox's features/performance.

Try opening it up, cleaning it out, and checking if the wires are properly connected. I'd recommend some compressed air to clean out the gears for the disk tray.

my xbox has a mind of its own as well. when i open the tray, 5 secs later it closes on its own :O

E-T wrote if it's standing up and falls it would brake your disk, and you cannot fix it, so be careful when your standing it up

hes not kidding it has done it to me several times

i have it sitting down and i never have this problem, i had it on my elite when it was standing up.

I heard that if your Xbox is laying down, it gets hotter; but I don't actually know if that's true or not.

My xbox has been laying down, and I've had it up for a while, but t just feels awkward when putting the discs in.

I heard (only heard) That laying it on the side screws it up and makes the dvd drive have problems every now and then. mine stands up and it is about 5 years old and has some drive problems. But I just apply some pressure to the top of the xbox where the dvd tray is and it opens up perfectly

It doesnt really matter. But i think an xbox laying down does better. Its easier to get the disk in and out.

Had it 5 years standing up and not one laser disc burn.