e200 rough idle in the morning

my e class e200 on a 1998 plate seems to have a rough idle when i start it in the morning if i dont hold the revs at 1500 revs or there abouts for about a minute the car seems to stall or if it doesnt stall the revs drop so low that the engine gives out a clunck sound like the ignition is retarding
does anyone know what is wrong with my car

few things to look for~~poor wiring to engine sensors~engine coolant temp sensor faulty,~throttle possition sensor(if fitted)~poor air/vac lines,(leaking).fuel leak back.

I was going to start by replacing the fuel temp sensor but cant find it on the e200 any ideas where it is the car seems to be fine once the revs have been held for a minute, but why does it make a clunck sound
how can i check the throttle position sensor
whilst this problem is taking place and i start to drive the car i can put my foot down bit the car will not respond any further the power/speed stays constant.

anyone please
when you refer to the tps is it faulty as when car is cold i put my foot down it just wont accelerate you can even hear a knock sometimes