I have noticed that when I am barefoot and gently rub my finger over the metal surfaces of the laptop that I feel a slight fuzziness as if there is stray voltage going through me. It is not a shock per se and the sensation goes away when the charger is unplugged.I assume the floor is bare concrete or maybe some type of conductive tile. Concrete is conductive. Especially when poured on grade, earth.
I believe what you are experiencing is a very low level electrical shock. Your body may be sensitive to low levels of electrical current passing through it.
Just a guess a difference of potential exists between the laptop and the concrete floor. I would suggest you wear slippers on your feet or some other type of insulator