steering problem

I have a 1999 A4 Jetta with 5speed. It has approximately 145k miles. It just started having a problem with steering. When the car is at a stop, or moving at a very slow speed, the steering is very heavy. It feels like both the tires are flat, or similar to turning the wheel with the engine not running. I checked the steering fluid when it was cold, and it was just below the minimum mark. My service manual says that is where it should be. Any ideas?

Yup, check it when it's hot and running.

Thanks, I'll give that a try when I get home from work in the morning.