My male colleague keeps randomly rubbing my shoulders. Last week I was sitting eating my lunch (I'd had a stressful morning) and he came up behind me and gave me a full on shoulder rub. This is probably the 3rd or 4th time that's happened since January. On other occasions he's squeezed my shoulder and rubbed it when saying thanks for something or mid conversation. I don't really mind it (in fact quite like it) but it's not really normal is it? We're quite good friends outside of work but could he maybe like me more than that?