1987 300E warm up problem
 

Hello Im new here so try to cut me some slack. I just bought my first merc. and so far I really like it. Got it for $3000 with 196,000 mi and is in perfect condition. I even have every receipt from 1987 till now. When I start it no matter if it has been driven or in the morning it is sluggish to get going. My first thought was a fuel injection problem or fuel pump but after a few miles it runs perfect.?? Can anyone give me a idea before I start spending money where i do not need to. Thanks in advance
Chris