Ever since I was a child, I have been able to "discharge" static electricity in clothing by touching it. The static falls out immediately! As a child my mother would have me touch all the laundry fresh out of the dryer and bam! All the static would disappear! If a friend has a clingy, static-y skirt, for example, I can grab it gently in a few places and after an unpainful little zap sound (and sometimes silently) all the static electricity is gone. How is this possible? I have never found anyone who could answer!
Perhaps you have naturally conductive skin - a little bit of conductivity goes a long way to discharge static. Depending on how much static is built up, you may also need to have some path to "lose" the electricity - maybe your choice of footwear? Finally - you must not hate (maybe you don't feel) the little "zap". It's not just a sound - you should actually feel it. But maybe you don't.
This also happens when your body heats up a lot. You must be having higher than normal body temperature. This causes higher conductivity causing electric charge. All our bodies create electrical energy for work and functioning of organs. Our nervous system itself also discharges electrical impulses. Due to high temperature more electricity is discharged from within the body to our our outer cells i.e. hands and legs, which gets discharged on coming in contact with a conductor. This used to happen to me as well, that's when I found this info.