Sometimes car won't start.

What is your question?

Sits for 2 days won't start. I jump it with a cheap jump set-up bam, off it goes. Drive car every day starts 95% of the time. Lights bright & everything. Today wife comes home from work at 2 pm (we are retired but need to work some) shuts car off. Has meeting at church at 8pm, car starts. Drives 10 minutes to meeting. In meeting for and an hour. Go to come home car won't start? I go and jump it with cheap set-up. As soon as I hook up battery cars starts immediately. What the heck............. Thank you for listening.

What makes this problem better or worse?

nothing

How long has your 2007 Mercedes-Benz CLK350 had this problem?

about 6 months