I can find INTJs more socially awkward (if that is possible!) than INTPs.. as a result, they can be seen as withdrawn or concentrate on what they are comfortable with ie their current hobby / favourite sci-fi etc.
It's also worth remembering that they face the world with Te which is bound to be less "fun" to behold than Ne. It doesnt mean there isn't a world of fun inside their heads but they dont externalise this world of possibilities like a perceptive intuitive does such as an INTP.
As a result, I find I identify more with INTPs.. and even find them more interesting - it's that Ne interface... but I have a couple of INTJs who have ended up by far the more sustained and firm friends. Once one breaks through the Te coldness, they are genuinely enthusiastic about the things that interest them.
I know that I'm totally boring to other people...and it's mainly because I (like Misty_Mountain_Rose said) either forget what I like during social engagements or I don't think others will be interested in what I like (like the OP said). It's been a full semester and the people that I've been around most don't know anything about my interests, while I know a lot about theirs. I don't like to externalize what I think is really interesting, so unless I drop hints, people tend to assume that I'm a philistine.
But I'm not sure if I'm INTP or INTJ (or something else), so...