Hi, on my '87 300TD got a problem that car would not start in Park, but it starts fine in Neutral; it is not always; usually first thing in the morning while it will be starting fine in Park after it was used that day...
I guess it would be safety switch issue, but would like to check if it might be something else or what is the right procedure to troubleshoot.

PS. Just replaced the bushings on the shifter rod, so it is nice and tight now, but this did not fix/help the problem.

Be sure the shift linkage is adjusted properly. PO might have monkeyed with the adjustment nuts to compensate for bad shifter bushings.

On the 124 the transmission controls the detents (the operator's handle flops like a fish when disconnected from the transmission).

Since the operator lever pivots in the center, pushing the operators handle to P causes the selector lever on the transmission to go all the way rearward.

I would make sure the transmission end of the linkage is solidly in the P position with the rod disconnected then attempt to crank the car. If it cranks then your NSS is good and the linkage needs to be adjusted. I think you could be hitting the mechanical end of travel on the operator lever when going to P but the lever on the transmission isn't quite to the right place.

VStech and I went through this on mine, it is a 2 man job, one to be under the car adjusting the linkage and the other to move the lever through the various positions.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech