HELP! Smell of oil in cabin of 300E

[Esquire]

Greetings,

On some occasions, after coming off the highway, and stopping at a light - I have had the smell of oil in the cabin. This was not the smel of oil - burned through an engine - but rather the smell of oil that had dripped on something hot - i.e., exhaust manifold.

It does not happen on ANY regular intervals - or circumstance, except that I will smell it once or twice during a drive - usually after having driven the car - after a cold (first) start - for about 15 minutes. **granted my climate control is on -- bringing me heat into the cabin. However, I do not feel that this is simply "in the air"

Any guess as to what this might be?
Anyone had this problem before.

Thanks
David