An amygdala hijack is normally perceived as an instant response to a situation that dies down pretty quickly when the thinking brain or neo-cortex kicks in and brings a calmer consideration and perception of the circumstances. It is the neo-cortex that says 'Oh my goodness what was I thinking?' Er, you weren't, that was the problem.
Mark Twain said that a lie can be half way around the world before the truth gets its boots on and that can be the relationship between the thinking mind and the emotions in the midst of an amygdala hijack. One reason for this is that the amygdala is like the sprinter kneeling in the blocks while the neo-cortex is sitting with its feet up reading a book - focussed on thinking and not reacting.
Once an emotional starting pistol goes bang the amygdala is off down the track while the neo-cortex says 'what was that noise?' And what keeps people in that emotionally 'set' position is a constant barrage of perceived potential dangers - 'physical', financial, personal, whatever.
Instead of having a gun in your holster in case of a threat it is permanently in your hand with the trigger cocked and so when a Problem-Reaction-Solution scenario is played out most of the population is already primed because of what I will call a state of 'amygdala standby'.
You can liken this to being in a dark house that is said to be haunted and you jump or freeze when you hear a noise that normally wouldn't bother you. The amygdala standby, using the sprinter analogy, is permanently in a state of 'on your marks', even 'set', because of all the fear stimuli that it has to scan and assess in a world where the most abundant emotions - by design - are anxiety and fear.