Date registered: Mar 2005
Vehicle: '01-E320 & 02-ST2
Location: John 15:18-19
Mentioned: 0 Post(s)
Quoted: 35 Post(s)
Welcome. Please click user cp and edit details to add your vehicle and location to your profile, it's often helpful information when you're seeking assistance.
You posted into the general forum, which as the name suggests is generic information across all models. There is a forum specific to your car, the W210. If you scroll down the main forum page you'll find it in the sedans section.
However, the first/best thing to do is have the codes read. There are lots and lots of possibilities, and that's what the codes are for. Otherwise you are just guessing and that can get very expensive and frustrating very quickly. If you haven't done plugs, you're due for them, and worn plugs could cause this, as could a vacuum leak, bad wires, plugged cats, bad MAF, bad coil....etc. (Again...getting the codes will narrow this down.)
The K40 relay has rarely been an issue in the W210, though.
Some auto parts stores here will read them for free, call a few around you, or you can buy a basic code reader on amazon for US$30.
Once you get the codes, you can look them up on the list that is posted in the W210 forum stickies.
Good luck and Happy New Year.
Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy; its inherent virtue is the equal sharing of misery. (Winston Churchill)