Put a fresh battery in it.

How are you noticing the 8Volts on the instrament panel or a meter?

Possible your battery is just gone. Or you have a bad alt that doesn't charge it anymore.(BTW the regulator is in the alternator).

Either way if the battery is NOT fully charged your not going to start because there is not enough power for the ECM to check and control the system. You may end up causing damage to your electrical components without a fully charged battery. Even if it is new with a 8 volt reading I would put it on a charger or go get a fresh one.
If it's old just get a new one.

 

As I mentioned, a dedicated battery store have the proper equipment to do a real load test, you'd be shocked how many batteries have been misdiagnosed..here's a PDF link that explains a few battery maintenance procedures:
http://www.autoshop101.com/forms/hweb4.pdf

 

With the doors closed and a meter on the battery with no accessories turned on, the battery should read 12.X volts. If the reading is lower than that, replace the battery or charge it and try again. If it is 12.X volts, just turn on the headlights and take another reading. Less than 12V is a problem, esp. if it dips down to 8V. On a tired battery 11.X might be acceptable. You mention that the voltage creeps upward to 12V after a while. This sounds like the battery is under load (like a car door is open while you're testing it), and again, would indicate a bad battery. Since it's a 2001, it probably should have been through about 2 batteries already anyhow...Clicking of the starter relay as you describe is normally related to battery issues.

 

Listen to these guys --- Your symptoms strongly suggest a bad battery...

Get the vehicle started and take it to a place like Auto Zone or whatever and have them run a diagnostic check on your whole system. It is easy -- they can check the battery and charging system.

If you don't want to start the car pull the battery and take it to one of those places to get it charged and checked.

BTW the reccomedation to check the wires, terminals and block to chassie ground wire were also right on. DO IT!

 

That is why AAA membership is useful, in that they include roadside assistance with their membership. If they are unable to start your car they will tow up to a certain maximum number of miles to a repair station or your driveway. Once the car is in your driveway, then you may spend a few months getting it started.
In particular, the newer Audi make servicing the alternator and starter rather difficult as compared to that of the C4 chassis.