I have recently been having starting problems w/ my '91 560 SEL. To start the car I have to now crank the starter for a much longer time and the car starts very hesitantly w/ noticeably higher smoke and a strong smell of unburnt fuel from the exhaust. The car runs just fine after it starts. Also, the first start in the morning seems easier than the ones after that. Seems like the air fuel mixture is too rich in fuel for some reason. The car has 111k miles on it and I got it serviced at 105K from a dealer. Any suggestions??