It could be your spine. You say it happens around the same time at night. I had chronic nerve pain for many years and at night it was worst. I dealt with it for eight years, I got an inversion table and stretched out on it and in about three weeks my pain with away and I was a hopeless wreck. I was also seeing a chiropractor. Hope this helps!
Your family doctor might want to check you out just to be on the safe side . In the meantime , it might help you to drink a cup or two of hot tea before bedtime to relax you ; but you shouldn't eat before bedtime . There are all sorts of caffeine-free sleepytime teas or calm teas that might help you . There might be some stress you are feeling from the past or present that could be causing your panic attacks .Also , I read effects of alcohol on the body can be devastating and heavy drinkers experience panic attacks as well .Or it could be anxiety disorder . Your doctor may be able to treat it successfully if you talk to him about it .Good luck .