Strange experience with the Navi. At startup, it luminates then goes dark. All radio functions are okay but no display. I drive for about 3 minutes and the display comes back on and is fine. It has happened twice in the last 2 days after a morning startup and it happened once about 3 months ago. I bought the X in November and the original owner had the battery changed about a year ago so I'm pretty sure it's not a battery issue. Any thoughts?

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'03 Carbon Black M5
'04 Silver X5 4.4
'04 MB SL500