RepairPal Certified shops can diagnose and repair your 2000 BMW 528i. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
You may have a Speed Sensor that is worn out. A god scan tool will tell you what is going on. Do you have a Check Engine Light on by chance?
here are some shops if you need help: http://repairpal.com/bmw-repair-in-baltimore-maryland