Things the boyfriend does that I don’t understand. .

So this may end up as a part 1.
But the current query is as follows. .
  I’ve been living with my bf for almost a year.  He’s not very physical at home, but he gets touchy in public and it weirds me out. If it wasn’t a total switch,  it’d be less odd, but because of my inexperience,  I want to ask if other dudes do this and why? Just before I ask him so that i don’t approach the question in an insensitive manner; because guys get really weird over that shit.