1999 s320 mercedes benz check engine light

Sounds like you have some blown fuses. That happens sometimes when the battery is being boosted. Recommend the boosting vehicle shut off the engine befor hooking up. The radio will have to be coded to come back on. Have the alternator tested as well. Could explain windows moving slowly.

Check your engines earthing straps for tightness and corrosion, P.s try to avoid boosting the battery direct on this vehicle, there is a boosting point point under the bonnet usually on the left hand inner fender. it is a black plastic matchbox sized box with a '+' in red on the flip up lid; connect the positive lead here and the negative lead to an engine earth point.