I have always felt out of step with people. I can smile and greet people and sort of go with the flow, but there is something more fundamental that just doesn't often connect.
I don't know why I didn't catch this post initially, but I definitely feel this way as well.
There is definitely some similarity in what you describe. I'm not entirely sure regarding the last paragraph, except that there are certain topics i instinctively avoid with certain people because i know it will it will reveal a deep schism.
I often feel I can 'get along' with most people I encounter, and I can certainly talk to them about what's going on in their lives, and can relate to them on an emotional level - as in the emotions they might be experiencing - but can't necessarily relate/empathize with the trigger/circumstance that caused the emotion (because I think we all have rather unique triggers).
But from personal experience, I suppose from the middle years on, when I've tried to open up, people either don't respond, don't know how to respond, *blow me off as being too serious - i.e. 'You're a killjoy'*, completely ditch me as a friend (this happened twice in my middle yrs -- I wasn't 'cool' enough all of a sudden - hence, I suppose I have quite a lingering fear of opening up to people) or give me a blank stare, so I then hurriedly change the subject or laugh it off or make a joke out of it. Or something like that.

I guess, my really expressing myself and my beliefs...has not proved to be safe in the past. So I don't really do it much anymore, in real life, and I just lend an ear to other people. By the way, I'm not writing this paragraph as a 'woe is me/pity-party' paragraph..more just stating what's happened to me historically.
So I guess that's why I feel I don't 'relate' to people -- not in that I can't get along with, or understand where people are coming from on a logical level -- but rather that I rarely meet someone who shares a similar life-view/perception view/processing of thoughts as me!!! It does take time to get to that level with anyone, though. I do have a handful of friends in my life, though, that are very precious to me.
And to clarify - on the surface, I can, and do, get along with most types, and I feel that I'm friendly both at work, and in a few of my extracurricular activities. But, I certainly don't bare my soul, so to speak..because that would be just plain silly!
And yes, this fear in opening up is rather self-fulfilling...if I don't open up, I might miss the opportunity of meeting someone who actually WOULD appreciate me -- so, this is something I'm going to try to work on. Carefully. ;-)
Would this also be similar though for most INxx's?? That we all only open up to a select, carefully chosen, few? I'm not sure it would be restricted to INFJ????