'92 500SL Strange Starting Problem
 

This is intermittant so I know it will loan itself to speculation but that is OK!

Here goes!

My son picked up a '92 500SL from a lady, I guess to go with his 560SL, who knows. At any rate, after going through all of the normal maintenance stuff and attempts at resolving, the car has a start up issue. What happens is that it's not that it will not start, it's that sometimes when you turn the key it turns over as if it is not going to start. (Weak start, generally first start in AM or after sitiing awhile) But, when you click it off and attempt a start, it turns right over.
The previous owner indicated that the car had always done this since she bought it in 1994.

Have taken it to a couple mechanics. Obviously it will not do it when they have it!

Changed out fuel filter, cleaned plugs, checked injectors, changed out air filter, replaced two air tubes that run down sides of engine.

Anyone had the same problem?

Ignition switch;
2 rows of rounded contacts, because the round buttons have so little actual contact with each other, it will give you problems. You just need the contacts, not the switch. I had many weird symtoms and all were solved with this one replacement.
Luck........