Mercedes 6.9 Intermittently Doesn't Start
 

Recently my car has been intermittently failing to start. I turn the key to run and lights, power, everything come on like normal, but when I go to crank it, the car doesn't turn over. Not even a click or a groan, nothing at all. When I fiddle with the shifter and move the car though some gears, it eventually starts. This last time, I had the car in drive and it started (is it supposed to be able to do that?). Is this a problem with the starter? I've also read that the ballast resistor can cause starting problems too.

Based on description the fault may be:

1) Worn out or missing bushings in the selector linkage.
2) A failing neutral safety switch.

Does the neutral safety switch also control the reverse lights? Perhaps that would also explain why they don't light up when the car is shifted into reverse.

Yes