The late Niki Lauda had three Formula 1 championships on his resume, but not every race car Lauda drove was a single-seater. Part of an RM Sotheby’s auction in St. Moritz, Switzerland, scheduled for Sept. 15, is this 1984 Mercedes-Benz 190 E 2.3-16, from the Race of Champions at the Nürburgring. The race was a one-off event held by Mercedes…