Rough idle only when cold, no CEL, no codes

Question by racheltan posted 5 months 1 week ago in Mercedes-Benz

I have a 2001 c200 kompressor, which lately had a rough idle issue when I start it from cold, which goes away significantly once the car is put into drive. No CEL, no stored or pending fault codes either. Took it to the mechanics, and after testing the only fault description that came up was 'unknown fault'. Car doesnt stall, mpg is fine and there is no loss of power at all. At wits end as to what may possibly be wrong with the car?