I had something like this a few months ago on my '07 328i. Turns out it was an oil leak at the valve cover gasket. It was at a spot where the oil dripped onto a hot engine part (exhaust, I think) which made it burn. I had it fixed under CPO, but the fix failed and they had to replace the gasket again this month after my digital dipstick went down two notches. They found another leak from when my lifters were replaced for engine ticking a few years ago, which they also covered.
Originally Posted by BMWUltimateDriv3r
But there was no smell. The "smoke" was also intermittent, sometimes appearing, sometimes not. It also did not seem to be coming from the exhaust of cars around me. I checked the hood and there doesn't seem to be any damage but I'm far from an expert. Any explanations?