I'd agree with Larry. Whatever the cause is,you have a lean condition. When the "pop" comes from the intake,its a lean or poorly atomized mixture. When it comes from the exhaust,its too rich.
I had a 78 230 for a few years that had a similar problem when it was cold. Since it went away after warm-up I figured it was just fuel condensing on the cold surfaces inside the intake. Eventually I took the intake manifold off and found a large chunk of carbon where the EGR connected to the manifold. I cleaned it out and the car was fine afterward. I figure the carbon chunk was soaking up fuel like a sponge(okay,a hard black sponge)when the car was first started.
ASE Master Tech
Mercedes Tech 19 Years