I'll try to keep it short and sweet:

I purchased my 96 A6 (2.8) about a year and a half ago. The issue that I'm experiencing is this: while driving, the red coolant light will flash (sometimes with no sound). Once it does this, I immediately pull over to see if the reservoir is full. If, it's empty, I refill it with either coolant, or water. However, recently, I've checked the level, and it has been at the correct level! After I allow the engine to cool down, I untwist the reservoir cap and the strangest thing occurs: the coolant level will sink to the point that it appears empty, then it will rise back up. It does this for about a minute. If the action stops with the level at the normal level, I'll continue to drive. After continuing to drive for a few miles, the light flashes again and the reservoir will be completely empty. This is quite puzzling.

If it is the water pump, I know that's a tricky fix. I have no plans on doing it myself. Any tips or feedback will be appreciated.