UPDATE 10/12/21

I've taken the car to a mechanic and he's got someone who specializes in Mercedes/Chrysler electronics.
The mechanic has told me that he thinks it's the cars computer system. He told me that the computer system is non-replaceable as it's programmed to the particular car.

I'm trying to figure out what the price is if the car can still be fixed so I'm still wondering if he means the SKREEM module, PCM, or something else.
He's replaced the Relay Control Module entirely, but that only allowed the car to start once and run rough, but not start again.