Yeah I have this shit, either touch or sounds make me startle. It goes back to my teens when my peers discovered any arm swinging near my head area would trigger a fight or flight response from me, like I was subconsciouly prepared for violence. Back then I hadnt AF yet, but you can trace some of my sympathetic dominance to the few but traumatic beatings that I received from my father as a child.
I think its better now, though. I try to become calmer everyday and remove any stressful person,activity,substance etc and flirt with meditation and creative yoga at times. I think all the tired but wired types we should investigate calming adaptogens and thats one thing I am doing.