Thanks to everyone for the helps.
I studied the throttle control a little bit today, I am afraid that the problem is not the throttle linkage.
As you all know, M119 uses LH injection system, the throttle body and throttle actuator are in one piece, the throttle linkage between the throttle body and cable is a hard connection, preloaded with spring. If throttle linkage or cable is stuck, there should be noticeable difference in the gas pedal feel, in my case, when problem happened the gas pedal still had normal linear feel, so it's very likely that the problem is either throttle actuator or LH injection computer system. The throttle Linkage and cable was lubricated 6 months ago with Mobil-1 ATF, it moves freely.
The problem is basically very high idle, >4000 in P, approx. 2500 in D, twice it all happened approx. 5 minutes after extreme cold start, just after coolant temperature reached 80C, which is the nominal operating temperature, coincidentally, according to the service CD, LH injection system changes its mechanism after engine reaches 80C.
Tomorrow, I will do some test on my driveway, just simply warm up the car in "P", see if idle changes.
I was planning to keep this car for 5 more years, and had been enjoying the cheerful moment each times I drove it, even after all the troubles: brittle wiring harness, leaky Power steering pump, leaky camshaft seal, dead Becker stereo, malfunctioning alarm/power seat/sunroof, mysterious shake and other small things here and there, but after this scary experience, I don't know if I still have the times/money/courage to keep it running.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.