Dead battery 2nd time I start the car

[Jrzy boy 7]

I am a brand newbie so I apologize if I screw anything up. I have a CPO 2008 535i and in general love the car. I have had a really weird thing happen twice in the last month or so and no one has any answers. I have parked at airport parking lot about a month ago, car sat for about 5 days and it started fine. Went to grocery store from the lot and battery was dead. Got a jump start and no problems since.
Just got back from airport six days ago, parked valet so the valet guy started it to have it ready for me and he turned the car off. Got my stuff in and went to start the car, lo and behold dead battery. Got it jump started and no problems since.

Anyone ever experience anything similar and how did you get it resolved? Your responses are appreciated.

[fussellb]

I had a similar problem and finally BMW ruled the battery defective and replaced it. Now I have an intermittent starting problem instead.

[Jack Dabsy]

I would suspect the alternator has critters inside LOL... Seriously, While the motor is stood for some time - the critters don't realise where they are going and might create a web/homestead in there... Also could be a Dirty MAF issue !!
Just a thought !