1991 Other Mercedes Benz Models Near Stall Starting up from

I have a 1991 Mercedes Benz 300SL. During the summer I experience a "near stall" when starting up from a stop sign or red light. The car sputters and nearly stalls when asked to move forward from an idle. This lasts about 5 seconds and then the engine seems to "catch" and takes off. This happens only when the ambient temperature is over about 80 degrees...yes, it runs great in the winter!

I hope someone has some ideas. My dealer has none...thanks!

CBJ625