((coconut))
I think I have had every kind of moment in therapy. (Until something new happens!)
Shutting down is a protective mechanism; maybe you felt like T was intruding? I think that shutting down is probably the "freeze" response to trauma. We react in three ways, fight, flight, or freeze. I have had many sessions where T and I inadvertently recreated trauma situations from my childhood so it might be worth noticing if the interaction reminds you of anything. This is especially true if your trauma history is complex.
I would definitely try to discuss this with T. Be specific and tell T about the shutting down and how it made you feel. Take your time with this. From my experience, there is no need to quit, but there is a need to slow down the process a whole lot.
Take care, and good luck.