I have had my 2016 for about a week. I have never had a car with eco mode before. I don't like it. Every time I start the vehicle I put it into sport mode. However it still randomly shuts off when I stop. Why is it doing this and more importantly how do I get it to stop?

When the car is shut off and restarted, it reverts to Eco mode because that's how Mercedes-Benz designed it to operate. To my knowledge, there is no way to change this default selection upon startup.