I have a 2018 Mini Cooper Hatch with the new seven-speed auto. I noticed that whenever I park the car on a slope (the front of the car facing downhill) it tends to shudder when starting the car, and shudders again quite abruptly when you shift the gear into reverse. I have Googled the problem and someone suggested engaging the handbrake first, then shifting into neutral, releasing the foot brake and then shifting into Park, but that didn’t solve the problem.
You should use the park brake when leaving the car parked, and always engage the gear before releasing the brake to drive away. If it continues to shudder after doing this, have the gearbox checked, it could a problem with the clutches, or the hill-hold might need adjusting, or it might be fixed by a transmission oil change.