Odometer goes black..intermittent
 

My odometer on my 1998 A4 2.8QM will occasionally not illuminate when I start the car. It will usually go on within 5 minutes or so but sometimes not. It has happened a few times in the past few weeks. I cannot tell whether it actually stops working (counting) or whether it just stops showing.

Any ideas into what's going on here? I have an appointment for the car next week and it would be nice to have some sort of idea.

Thanks

Tyler
1998 A4 2.8QM