Does it happen around 3 in the morning? I know that there are studies that say that at 3 am, the body does something that sometimes processes cortisol. It sounds like your autonomic nervous system has something going on. That is the fight/flight/freeze part of us. I know that I wake up at 3 quite often. I have adrenaline surges during the day sometimes, but I know mine comes from trauma and survival skills that my body has developed from childhood.