Very Sluggish at low speeds on 1990 Mercedes-Benz 300SE

Most of the time when you take off in it from a stop the harder you push the gas pedal the more bogged down it seems to get. Once in a while you can get a really good start. Also whenever you go less than 35-40mph the check engine light is on but if you go faster for awhile it turns off. It seems to accelerate normally if you are above 35-40.

Asked by for the 1990 Mercedes-Benz 300SE