Brakes; low pressure before starting

[asbury@northpole.med.uvm.edu (Jamie Asbury)]

To anyone interested:

I have a 1984 Audi 5000s, 4 door, fuel injected sedan just recently bought.
There seems to be a problem with brake pressure when the car is off.  In
the morning, the brakes go to the floor and hit a stop (I assume it is a
stop in the master cylinder).  After starting the car and lightly pumping
the brakes for about 2 minutes, full pressure returns.  The brake pressure
is fine while driving or when the car stays on.  

Is this normal brake function for this car?
If not, can the pressure accumulator be the problem?  Is there an easy way
to check for leaks, which could possibly lead to lose of pressure over a
long period?
Can the master cylinder be the problem, but still allow for normal brake
operation while driving?
Could the problem be air in the brake system? 
If anyone has any ideas or comments about a solution, please let me know.
Thanks
Jamie