From my personal experience, I have a very good friend who tends to stare off into space whenever no one is talking to him. This tells me that he tends to have a lot of things racing through his mind most of the time. Whether it is work or his relationship. He also tends to press on the back of his neck often which seems to connect to his previous nonverbal habit and seems to be stress from everything going on in his life. These are some non-verbal habits that are not specific to him and I have seen other individuals do these things as well.
