No, trademark laws are what stop you from selling a counterfeit Mercedes or BMW. A design patent would stop you from selling a car that looked vaguely like an existing Mercedes or BMW.
In the case of a counterfeit that looks like a BMW and is badged with the BMW logo, sure.
Otherwise, it becomes a matter of trade dress, which is equally important – and equally valid. Which, for this example, could be a "BBW," perhaps, with green and black circular emblem and a design resembling a Z4.
The test, as I understand it, is whether or not the manufacturer selected a given design specifically to piggyback on the existing goodwill of another brand.
Design patents are what stop you from making and selling your own counterfeit Mercedes or BMW, for instance.
Neither company pretends to own a patent on the wheel, and Apple isn't claiming ownership of rectangles or rounded corners.