I purchased a 1993 Mercedes 300D about a year ago. Car has always shifted quirky in that if leave it in drive it will go from second to fourth missing third. I “rectified” that issue by keeping it in D-3 and when it gets to third have put it in drive to go to forth gear. I have driven car about 40000 miles total-and within last few months the car shifts fine from second to third when it is cold and in the initial stages of warming up. As the car gets to operating temperature I have to rev car to 4000-4500 rpm and then let foot off pedal slightly for it to shift into third gear then it shifts perfectly from third to fourth. A few times it would not shift even with revving method. Money has been tight but know need to bring it to independent shop that would work on these cars. Wondered if anyone has ideas about the nature of the problem.