All great suggestions, but the behavior I'm experiencing doesn't seem to quite fit. If the MAF was dirty, then the car should still be able to start, but stall out and/or sputter -either while starting or idling. At least that's the behavior my father's Mercedes ML320 exhibits. ...granted they're completely different makes.

Temps weren't cold enough for anything to freeze (3/4 times, temps were > freezing). Also, if the plugs were bad, the engine would exhibit a loss of power (pistons not firing) while running.

The behavior I'm experiencing really seems like it's computer related. When the car doesn't start, it doesn't even provide a hint of starting. It just turns over. And the two times it cut out, the engine just stopped. If sensors were bad or dirty, there would be some combustion -as well as a check engine light. In the 335's when the HPFP (High Pressure Fuel Pumps) fail, the engine sputters while it cranks, starts, idles poorly and stalls out. When MAF sensors are dirty or have buildup, the temperature of the thermistor or hotwire in the sensor would provide a false reading, which would allow the engine to run, but very poorly (see http://www.autoshop101.com/forms/h34.pdf).

You're entirely right about the plugs. If they're dead (most or all), then I'd have the same behavior (not starting), but the car runs totally fine otherwise. It's a very unpredictable problem and one that I can't re-create on command. Also, its not constant. The car starts up and runs 97% of the time and has only failed to start 4x in the past 5+ months --and all just recently over the past 2 months.

I'm not trying to shoot you down, I'm just thinking through the problem, symptoms and possible causes to make sure the forum has as much info as possible. Thanks, and please correct me if I'm off base on any of my statements.