Welcome to Android Central! How close is your finger to the screen when the touch registers? If it's just a couple millimeters, I wonder if it has to do with static electricity--a big enough field might be enough to register a touch. How can a screen sense touch? A basic understanding of touch panels | EIZO
If you notice this behavior, see what happens after touching a grounded metal object, which should discharge any static electrical field that might have built up on your skin.