You are having a problem related to the IR system. (Infra Red)Lock /alarm and ignition. I'm not sure which causes which.
On the 97 S320 I fixed with these same symtoms the problem was the ignition switch. We presumed the various connections for ign term 15 were not activating. We caught the basic starting problem as a lack of IR activation signal to the engine management controller (through the scanner). The problem was that the IR system was not getting power.
The way I caught the activity was that as I was hooking up the scanner I turned the ignition key to the run position but the dash lights didn't light. I thought that I hadn't turned it far enough and turned it some more and the starter engaged and I released and the lights came on. I didn't recognize it the first time but I found that if I turned the key slowly to the start position I could get the dash lights to quit and the car didn't start in this condition.
This was a 140 chassis not a 210 chassis so it might not apply here.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by stevebfl (edited 05-14-2000).]