Sounds like a disc read fault - dirty lens or failed laser. Haven't had any issue with my X5 CD-Changer but I've seen this often in other units.

You could try cleaning the lens as a first step... opening up the player, not using a lens cleaning disc.

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Wayne
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)