It's not really static. It's actually induction of the transformer (probably to parts of its shielding) that can't be released to ground.
You can tell because it immediately disappears when you unplug it. Static electricity would take longer to build up. And generally will not build up in metal objects but rather in insulators.
You can tell because it immediately disappears when you unplug it. Static electricity would take longer to build up. And generally will not build up in metal objects but rather in insulators.