I pulled the car into garage, and realized it's not inside enough. So I moved the car forward, but forgot to place the shift to P position. With the shift in D position, I shut off the engine, opened the door, ready to get out. I did not notice the car was moving backward, until the open door hit the garage frame. I file a claim with my insurance, had the front door replaced in a local body shop. I confirmed that in D position, with engine shut off, the car can move freely in my drive way. I did have this issue in my other two cars, I occasionally forgot put the shift from D position to P position, but the car did not move. This issue - a car can move freely without driver's awareness - is a serious and dangerous issue. If this happens in the street, a serious crash can occur. The car manufacturer should figure a way to prevent this from happening when the shift is in D position and engine is shut off.