So this just started happening a few days ago. When I go out to my car in the morning the mirror (not the mirror housing) has moved and is pointed "in" as far as it will move. Since they are power mirrors I simple change the position but what is causing the mirror to move? Its really, really wierd...?

I believe it to be an auto dip feature. I hope to be corrected if mistaken, but I know a lot of high end cars carry such a feature that dips the side view mirrors down and in to help aid in parellel parking when going into reverse, but suspect it would revert back to its original position once put in drive.

I have that feature on my 98 XJR, but it is only for the passengers side.
As you said it only works with reverse engaged, and reverts to normal position when taken out of reverse.
But then again my car is UK spec, it may be different on US spec models.

I would imagine it must be programmed to that position, and goes there when you unlock the car. I would try re-programming it. Other than that, I have no idea because U.S. spec cars don't have the "dip" feature on the drivers (left) side, just on the right side, but only when you are in reverse, and press the mirror adjust switch.

I agree with Scott. Try to reprogram it. Use a different program button. Reset the seats and the mirrors to the right position. Then hit memory. That sets the seats, steering wheel and mirrors. Then with the car in reverse, program the right mirror for backing up. instructions are in the owners manual. Oops, in your case, the left mirror for backing up!

Also program your remote to the memory seat. Set seat wheel and mirror, hit memory then the unlock button on your fob. I would imagine you might notice the mirror moving when you unlock the car? That is a tell tell.

the wife drove the car yesterday and this problem seems fixed. Man, maybe she should use my Jag more often....

Has your wife got her own set of keys and remote for your Jag?
If she has it would prove the memory position theory.

nope...same set of keys