[s-cars] S4 Complete shutdown – please help

[joe smith]

Hello all – 
I have a 94 S4 with 150,XXX miles. Three days ago I drove to the market with my kids, returned home, all was well. The next morning I went to start the car and it was dead – no power at all, I figured one of the kids left a door open or flipped a light on and didn’t shut it off. I jumped it. Funny thing was, I attached the cables, got into the Audi and started it – it fired right up, no hesitation, not 30 seconds after I hooked up the cables it started like it had a full battery. I drove around the rest of the day, started and stopped several times, no issues. Could not listen to the radio, it was in safe mode.
Yesterday morning – I started the Audi - all was normal. Turned on the defrost front and rear – started loading the car for a little trip. Left it alone for 10 min – long enough for the car to get warm and melt all the frost – when I returned the engine was off, but all lights were on and blower still running. I got in and started again, fired right up – ran for 10 seconds and quit, all lights and blower were still on. Cycled the key to start again – and it was instantly completely dead. No lights – nothing, like one of the battery cables was removed. I did nothing – took the trip with another car. 
This morning – started like normal? Any thoughts?
Thanks,
Joe