More likely to be friction between you and some garment. Or some garment and your car's interior. May I suggest avoidng nylon underwear

Fleeces are also a problematic garment. Which is a pain as static is most prevalent during the winter when the air is dryer, ie when you want a fleece the most.

The good news is that static sensitive components are far less sensitive once they are in a circuit, and that it is highly unlikely that you would build up enough charge to build up the potential on the whole case (with respect to any non-grounded 'floating' signal) to do any damage.

But still, there are some precautions that you can take in times when static is prevalent. Touch something big and metal after any movement before you touch anything sensitive. Some cars (eg Mazda MX3) have a grounding contact on the door. Avoid touching electrical connections unneccesarily (eg serial port, LAN etc). If neccesary, keep yourself grounded while moving about. Avoid nylon/polyester based clothes.

Don't be paranoid about it - just exercise some common sense when required.