Yes, as this is a biological reaction you don't need to be aware of a conflict to experience it. That's what differentiates the term "neuroception" from "perception". And it can be triggered anytime for the first time. 
Although the soil is usually prepared in childhood, we can have UDIN moments all throughout our lives. But often it's not UDIN moments (original trauma) we have every day, but we trigger the same emotions and reactions from a conflict that was imprinted earlier and that sensitized us. By self-triggering I mean we can do it by our thoughts, beliefs and behaviour, as one can feel isolated even when there are loving people around, if we shut them out.