So my wife got stuck when the A4 wouldn't start. Lights come on, but it won't crank. So Im on my way to pick her up and she calls 10 minutes later saying that is cranked right up. We drove (I followed her) to Audi to get the 6 month old OEM battery replaced. The car started up fine 2x while there. We installed the new battery and left. She's driven it like 4x today and now calls me saying the car won't start. I leave home to go pick her up and 10 minutes later she calls to say it cranked and she's on her way home.

WTF? Any ideas? Thanks.