Are you a person that collects static electricity?
I am, and I get small shocks off my PT now and again because of it. I know its me, because I get shocks off the car door, shelves in supermarkets, you name it, if its metal I can get a shock off it. I can shock other people too.
You might want to consider rubber soled socks lol or more seriously a rubber mat. I've been thinking about getting rubber insoles to wear ...well everywhere tbh. I think a rubber mat of some kind might be more practical though. I get shocked in socks, shoes, bare feet, doesn't matter, but none of it is/contains rubber.