I just found this information:

THE CAR

• Clothes: To keep down static electricity, opt to
  wear natural fibers like cotton in the winter instead of synthetics like
  nylon or polyester. Synthetic fabric sliding along car seats can generate a substantial charge leading to those annoying static shocks.
• Fabric softener sheets: Once again, these handy
  sheets come to the rescue. Rub car seats with a dryer sheet every couple
  of weeks to reduce static cling and shocks.
• Metal: When exiting the the car, touch the handle before you slide across the seat. This will break up the charge instead
  of letting it build up. Also, before you enter the car, touch the metal
  door handle first with your keys or some other metal object. This
  technique will transfer the shock from metal to metal—and you won’t feel
  a thing. The “metal to metal” strategy can also be applied to household
  objects, such as doorknobs and kitchen towel racks using keys or
  silverware.

this used to happen to me all the time with my previous car, then when I changed cars it stopped happening, even though I used the same seat covers in the new one. I think the only thing that changed between cars was probably the carpet.

I get shocked when discharging myself! Many of my pockets contain softener sheets and they seem to work a little teeny tiny bit, but not like the static guard does. One of my dogs also has this problem. I use the static guard on her sofa as well. This past winter has not been as bad for us since I started using the static guard.

Please don't any of you come back with scientific evidence that static guard is a harmful product. I prefer to remain in blissful ignorance! :)

I see small pieces of chain hanging off bumpers or the undercarriage of vehicles that's what it's for. The chain makes contact with the ground and you avoid the shock. You might try an auto parts store for such a device. If you wear a ring tap the ring to it door handle before you grab it.

When I had the computer store we had a lot of issues with static in the wintertime when we had the store with the carpeting. I would take a spray bottle of water and mist the air and let it fall onto the carpet. Static doesn't like humidity so when humidity comes, static leaves. No need for static sprays, dryer sheets or anything like that. When you have static in your clothes, you've overdried them. Rather than using static sprays, mist them with a touch of water and give them a shake. And don't keep them in the dryer so long next time. And no, don't soak them! When you know there's static and don't want the "sting" when it zaps, open your whole hand to touch a metal object. It'll allow a larger area for the discharge so you won't feel it. I had to lecture people over and over when working with the computers to put your whole hand on the computer case, preferably near the power supply to discharge so they didn't damage the computers.

Rubber soles will insulate you from the ground so you're not going to be able to discharge through them. The static has to exit elsewhere.

You did not state when you get shocked. Is it when you prepare to exit the car, or is it when you are outside the car and approach it to touch the door handle? The causes in each case are different.

I will assume it is when you exit the car. You said that it did not happen with your former auto, but began with the current vehicle. A likely cause is a difference in seat and interior materials. Sliding out of the seat and lifting away can impart a goodly sized charge on your body. Its more noticeable in cold, dry air. There's more leakage with very humid conditions. I wear shoe-boots with crepe rubber soles. These are very good insulators and are very bad for allowing a static charge to build up and hold on my body - really bad if I'm handling computer memory modules. (When I do this, I take off, or change shoes and wear a grounding strap.)

Try anti-static treatment of your auto seat and interior materials. What you wear is factor also. Some fabrics are bigger charge producers than others. Much of the charge is generated when you lift away from a surface.

I always got shocks exiting the car with my previous car. Dragging my butt out of the cloth seat.

This one has leather interior, and never a shock now.

When you get out of your car, you should always touch the roof of the car to discharge static, prior to pumping gas.