Vintage Cars: 85 380se starting issues, electrical trace, air filter

Question
Ron,
My car has intermitent starting issues. when I turn the key, a brief (one to two second buzzing sound comes from under the air filter housing and the engine does not turn over. However when you get the tire jack and raise the chassis a few inches off the floor, the engine turns over and starts. I've had the contact points on the starter cleaned, another starter installed and the same problem happens. Ideas? Thanks, Mike

Answer
I wonder if you have a short somewhere that gets corrected when the car is placed in a twist??? Gotta admit this one is new to me, and I have seen alot.  Make sure your ground connection from the battery to the chassis is clean and good. It has to be electrical, trace all starting components from wires to relays, something is making a contact when the car is raised and not when it is on the ground
Let me know what you find