This was terrible for me in the early stages of benzo withdrawal, god i would literally jump to the roof when i heard a noise with intense fear!
I learnt to adapt and when I did jump or startle easy, I would reiterate to myself internally 'why did you just jump?' and sometimes try some humour like 'you're such a muppet' combined with mindfulness awareness and controlled medium breathing.. eventually this began reprogramming my mind to accept it not as a threat. I found taking something to try and calm down after it made things worse in the long run as my mind then started to learn that it if it startled, it would get a treat like theanine or something.
Pavlovs Dogs all over! Glad I did that pyschology class now :)