Exhause smell in cabin after stopping on 2005 Mercedes-Benz CLK320

Sometimes when I pull up to a stopsign there is a strong smell of (I guess) exhaust in the cabin. Not every time but frequent enough. Can't smell when getting out of car. No codes are showing and doesn't burn oil or have any leaks anywhere. ??

Asked by for the 2005 Mercedes-Benz CLK320
You may have a small oil leak that is leaking onto the engine block or the exhaust system. Has it been inspected thoroughly for leaks?