I am probably slightly above average height - 6'0" - but I once knew about a guy at my school who was really tall - like about 6'8" or so - and also have looked rather powerful in general, and I found myself feeling quite intimidated by him.
If we walked towards each other or wear about to walk through the same doorway i always stepped aside and allowed him space, and I also found myself looking up at him with large and timid eyes.

Is this something that usually happens to people?
And what would be a good explanation for this?