is this a protective instinct or is it more of "she's mine, back off" thing, or is it something else?
Most Helpful Guy
No.. it's neither affection nor marking territory. He desperately needs your attention and touching you is a subconscious method of holding your attention and focusing it on him.
It is also an indication of interest as you do not reject his touching you. If you told him to stop you may find yourself with less company in future nights.
Most Helpful Girl
No idea, but my ex used to do the same... probably just to show affection