you car has cloth-covered seats. You're also probably wearing clothing that contains artificial fibres.
What's happening is that you're acquiring a strong static charge by moving aroundon the car seat, and this is being discharged instantly as your hand is about to touch the metal object. I say "about to touch" because it's then that the high-voltage charge arcs across the small gap between hand and object, and you get that very unpleasant cracking sensation.
Next time you're about to leave the car, try this:-
Grab hold of some metal on the car BEFORE you set foot on the ground - perhaps by opening the door, and holding the metal frame that surrounds the window. Hold the door firmly, and then swing your leg out and put your foot on the ground. Step out of the car, still holding the frame, and you'll be fine - your static will be discharged painlessly.
The trick is to make sure you hold the metal door frame firmly - so no arcing can occur. You'll soon get the knack, and it will become a habit.