The parking pawl is released by hydraulic pressure that is created when the engine is running. The engine drives a hydraulic pump in the front of the M-DCT transmission. After starting the engine there needs to be enough transmission pressure created to disengage the parking pawl to allow the car to move.
If you are fast on the reverse selection after starting the engine you could have the condition you are describing.
Several factors might contribute to this also:
1. Length of time since the vehicle was last started (fluid drain back)
2. Fluid temperature (pressure build time)
3. Load on the pawl (parking on a slope where the pawl is holding the vehicle)
There also could be a chance that the fluid level is low. When the fluid is cold this would be a possible problem, but “cure itself” when the transmission fluid is warmed up.
Transmission fluid level changes with temperature.
This is a link for pictures of the parking pawl and description