Don hit the nail on the head!
When you slide across the car seat, you scrape up free electrons from the seat. If you do not ground your self while sliding, the charges build up in your body rapidly, which accumulate to create a large potential [voltage]. The car body is considered ground in this instance, however an actual ground connection is rarely required to discharge static charges [just scrape your feet on a carpet when the weather is prone to static, then touch another person. This should demonstrate this point!!].
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!