420SEL: Neutral Switch
 

Just paid $500 to get my car back. Various repairs, but most important thing was that car would not turn over from time to time and would strand me. Mechanic said he couldn't find a problem with the neutral switch, but when I tried to start it to leave work after picking it up at lunch the car would not turn over. Same problem. Tired of fooling around with this guy. Where is the switch located and how does one change it? Is there anything else that would cause the car to periodically not turn over? Battery is three years old but seems good, ie all lights are bright etc., When it does decide to turn over ( you can go back and try it an hour or so later and sometimes it starts) it turns over just fine.

Haven't had that problem on my Mercedes but have had it on 2 of my VW's. One was really sneaky - the negative wire to the battery from the starter was corroded inside the cable. After trying the usual things, a new cable solved the problem. You might want to use an ohm meter and check for resistance in the cables. The other VW did the same thing only this time it was the ignition switch wearing out - a new one corrected it. Have you tried jiggling the gear shifter slightly in and out of park or neutral to see if the engine starts to crank?? That might show if the neutral switch is intermittently not making contact. That is all I can suggest from my experiences

what year and how many miles you have?
it sounds like you need a starter. I have similar problem, I rebuild mine for less than $10.00. it turned out two of the four brushes were very short. You can DYI and get it rebuilt for about $60 at the shop.