Sorry had to repost this as a new thread as nobody would ever see my comment/question on the previous thread at #22

I have this happening on my 04 XJ8 and I dont think it's temperature related as I live in Los Angeles (although it does go down into the 40s some winter mornings Brrrr).

What does seem to affect it is the time between driving. I found that with daily driving the screen rolls a couple of times and then stops. but i just got into the car after a week of non driving and the damn thing has been rolling for a couple of minutes.

i am a bit confused when previous posters have mentioned the "head unit" and then discussed the center console removal. Isnt the head unit the thing in the trunk?

I think I will take a look in the trunk at where it connects to the unit first. Interesting how one was claimed to be cured by replacing the screen and another in an S Type was cured by changing a radio amplifier, what's that add up to I wonder?
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I would not touch the audio amplifier. The screen is driven by the navigation unit in the trunk. The nav unit sends analog video signal - very similar to what old computer used to sent to a monitor via the VGA cable.

The roll you see is loss of video signal sync, that would be pin 18 on the display or pin 1 on the nav unit. That cable does not go straight to the front screen, there is a harness in the middle (center console I would guess), but the schematics on the XJ is wrong to begin with so I would not trust which pin that cable should go to.

Now there could be a lot of reasons for the loss of video sync, bad or corroded connection is one of them, could also be a bad capacitor on either unit, given it gets better when it worms up.