Some incorrectly claim that the shocks are the result of discharging a static build-up on the car body – this is not the case. The static charge is built-up on your body as a result your interaction with the car seat material – and then discharged as you touch the car body.
The charge is built-up as a result of you getting up from the car seat. To avoid this resulting in a shock, whilst removing yourself from the car seat, ensure that you are in contact with a conductive part of the car which will result in any charge being discharged as it builds up, preventing any shock.