My 115/300d had the same problem. It also had a very slight fuel leak which turned out to be a leaking fuel delivery valve o-ring. Replaced the seals and no more problem.

If your fuel delivery seal/s are bad you can see them leak by pumping the priming pump and watching the top of the IP where the injection lines go in to the pump body. If you see the slightest glisten of fuel there then you have a leaking seal. It is a one hour job to replace them all. They cost about $3 each. I know, it is hightway robbery, but then they have them and you want them. Ain't capitalism great?