I feel I am reacting automatically and without nuance and my behavior becomes totally predictable and it seems to be related to things in my past more than what is actually going on in the moment. That is what I was using the word trigger to describe.

EDITED TO ADD: I dont' want to define the word 'trigger' for anyone else. Just let it be whatever popped into your mind when you read the title of the thread. I realize now there may be many definitions.