How do I turn off the door alarm when it sounds unintentionally?
press the unlock button on the key fob.
But why does the alarm go off?
Are you saying the car is reporting an open door, while you are driving? If so, it can be as simple as an adjustment of the switch that controls the alarm and the interior lights. When it happens try and check to see if the inside dome light is also on. If it is, make sure you tell that to whoever services the car for you.
Do any of the doors rattle a bit? Is there something stuck between the door and the car somewhere?