i have experienced this also .......
from a post i submitted earlier "went to look at an 83 300d t station wagon. manual sunroof. not all that bad looking really. but so slow. must have taken 10 seconds to accelerate to 20 mph. then all of a sudden the booger took off and was normal. but every start from stop was again so slow. what could cause such a condition? the man did say his wife did not like driving this car. no wonder why!"
i too am most familiar with the fuel burners as i have presently 4, 5 and 6 cylinder mercedes models.