I started the engine and a big puff of blue smoke appeared. It only happened once. on 2007 Mercedes-Benz SLK280

what would cause a big puff of blue smoke when starting the engine after sitting over night, it only happened once.!!

Asked by for the 2007 Mercedes-Benz SLK280
Usually this is a sign of the failed valve stem seals. Some oil sweeps through the seals and burns in the combustion chamber at the next start.