mercedes 200clk coupe petrol and gas 1998?

my car drives very well but after about 13 miles when i go to stop at the lights or i sit in traffic the engine drops power and some times cuts out this happens when it is in drive and N and i have to keep on stating it this happens about 3/4 times a day and some times it does not happen .there are no engine lights l have put in new plugs in and have cleaned all the air filters i have had some realy good advise from a member and done what he said but there was a few things that he said to look for but could not find them on the engine so could not check just can not work it out what else can i do i no that it is realy some thing miner. can any one help