In all previous cars, and other MBs, when you put the car in reverse and release the brake pedal the car will slightly start to roll back. In my newly purchased 2015 GLA the car doesn't move at all until I give it some gas. I read some of the threads about jarring and I don't have that issue. When I apply the gas it is smooth but it won't move an inch after release the brake from a cold start. Is this normal?