My Gwagon has been displaying red battery/Alternator light for about a month now. I have changed the alternator and battery yet the light is still on. Plus it jerks sometimes
You have not mentioned what model G Wagen you have?
The next step would be to check all wiring and terminals and also the ignition switch.
Below is a typical Mercedes wiring diagram for the alternator circuit.
I think you should have the B+ terminal checked at the alternator (if fitted); this is the alternator excitor allowing the alternator to charge and controls the dash pilot light for battery.
Jerking can be any thing; air filter, fouling spark plug, fuel issue etc, etc need more info.