- is self-admittedly introverted (thinks "people suck" but enjoys his friends and enjoys our co-workers as he's gotten to know them)
- is quick to respond to an issue (our line of work is fast paced and potentially hazardous and he rushes in as needed)
- is well put together aesthetically (sporty/outdoorsy and neat in his attire)
- finishes my sentences or questions at times (with varying accuracy)
- notices observable physical details (identifies things as a quality like "soft" by sight, smells things)
- observes without comment until necessary
- uses logic at the expense of emotion when administering discipline
- teaches by active physical example or instruction
- seems rather reserved but has initiated conversation regarding our mutual interest in our work
There's a good chance you're right. The archetypical ISTP uses Se to take in a lot of data and mentally sorts it out as impartially as possible. We favor action over words, which extends to how we prefer to learn and therefore teach. That also means we sometimes won't speak unless necessary. It can be jarring for others - once someone asked me if I have a quota on the number of words I'm allowed to speak each day. If a conversation doesn't interest us we'll be content to drift back into observation/data gathering or mentally process any info backlogged in our brain. If a topic piques our interest we'll likely gab for a good while about it. We're typically all on or all off.
When we have occasion to chat (despite my completely reserved nature at work it's easy to talk to him one-on-one), he is more of a question answerer than inquisitive. As time has passed I've been able to ask about his personal life and he's been more willing to share. He doesn't ask about my personal life.
We value our privacy and in turn respect that of others. He chose to be open about himself and likewise expects that to be a choice for yourself rather than an obligation.
I have seen him become frustrated and lose a bit of the handle he has on his emotions in two ways, once through slight anger and once through withdrawal that masked slight/anger. In both instances he resolved the conflict and returned to his usual state.
I don't know if other ISTPs would use this analogy but my emotions are like the steam in a kettle. My objectivity keeps a lid over my otherwise mercurial emotions but sometimes the pressure is too high. Either it leaks out or I zone out a bit to tighten the lid.
For some time, despite having already conversed with me, he would not say hello of his own volition.
I'm guilty of this. Typically it means I'm in my mind either sorting out ideas, zeroing in on a task, or recharging from being sociable earlier in the day.
In the midst of our work however, (our shared passion) he would make the effort to engage me, to ask how I was getting on or just make himself available for questions and to give instruction. He has also done this at the expense of his personal time, staying later than necessary in conversation.
Either he's a good supervisor who's trying to ensure his team member is integrating well or he's trying to spend more time with you personally.
He will smile now much more readily and he is a bit playful. He has made a few witty remarks (which I loved but he seemed to think he had to explain that he was only joking).
That's a bit unusual, though I might do that too if I'm teasing someone and I'm worried they'd interpret it as legitimate insult.
As an INFP I have obviously romanticized our interactions, but I wonder if I can put any credence in the perception I have that he may be interested in me as a woman. I'm not inclined to trust my intuition when it comes to men, I believe I'm simply infatuated again with someone who is lovely to look at and shares one of my primary passions. But I find that I see him more (as though he makes himself more visible) and we're engaging more with a more casual nature to our interactions.
Is this just an average ISTP work relationship?
There's not enough here to form a definitive conclusion. He may be interested but playing it slow and cautious, simply be polite and sociable,or is sending out mixed signals because he wary of office romance. Per ISTP protocols, more data would be needed.