I know an ENTP 7w6 sp (I'm thinking sp/sx). He comes off as more introverted than other ENTPs and other extraverts in general that I've known. He has more of a goofy Ne and can sometimes have the feel of a very cerebral INFP. Like the 7 sp/sx description describes, he withdraws not exactly to reflect but rather the opposite: to avoid or escape issues he doesn't want to address. Despite that fault, he's very well-liked and makes friends easily; people gravitate towards him. In relationships he tends to focus intensely on whatever person he's with at the time. I've jokingly called them his "girls of the moment," and that may not be entirely fair to him since I don't think he makes a conscious decision to set these girls apart from everyone else for a period of time then gets bored and moves on. I think he just picks certain people out whom he finds interesting and directs more attention, time, and energy towards them.