What it means when a guy touches your back?

So I'm having coffee with this guy and all the while we're talking about work and random stuff. Out of nowhere (while talking) he starts to gently stroke my back and also started to play with the fingers of my hand. This guy and I have met before purely on a professional basis, always discussing work and exchanging ideas (we don't work together but we know each other from years back). He always seemed so uninterested in me, but now I don't know. Any thoughts?