W126, MPG Products to Increase Mileage

My 1990 300SE runs fine normally but lately when I go out and start it it starts fine but if I drive a very short distance or kill it and try to resart it it turns over and sounds like it is mis-firing and won't start. This is happening more and more often but not every time. After I finally get it started it runs fine in park but if I put it in gear it sputters and dies this happens over and over and then eventually I can get it started and go. While it is doing this I can rev the engine up in park and it runs great but as soon as I put it in gear it dies.

Dear Friends!
I am an owner of MB 300SD 1982. Recently, the car presents disabling electrical issue which I hope to pin point eventually. There is a electrical surge somewhere under console ( I can hear climate control clicking) which drains all electric charge (battery). When it happens all my dashboard indicators go wild. Surprisangly, all fuses stay intact. I suspect it may be blower engine goes bad, but I am not sure. Anybody had this problem before?