Sitting in the car, electrostatic charges are generated on the car seat and the person’s body, due to contact and movement between the clothes and the seat. When the person leaves the seat, They take half of this charge with them. As they get out of the vehicle, their body voltages rises due to this charge - a voltage of 10,000 Volts is not unusual. When they reach to touch the vehicle door, the electrostatic discharge and shock occurs as their hand approaches the metal door.
I keep getting shocked when I leave my car. Sometimes I can see a little jolt of electricity when I shock Lily, right before she screams.