He is a gentle and nice person, contrary to popular opinion of a full of himself starlet. Maybe even too nice for football, and probably has to keep his guard up in the cutthroat environment, which then I guess gets interpreted as coldness or unfriendliness or whatever.
Same with selfishness, he is very much a team player by disposition, and talked of working on himself to become selfish when in form, learning from Robben etc. The perception also comes from playing with the latter, Lewandowski isn't completely selfless like T. Müller, and pays back when ignored.