A few weeks ago before going to bed my anxiety started to intensify. I could feel my heart pounding and started sweating profusely. Flashes of light in my vision. Intense (and I mean INTENSE) and spontaneous fear with no apparent trigger. Then there was a burning feeling in my chest and a pump like feeling in my abdomen. 
It eventually subsided after around an hour and I was able to sleep. 
The next morning when I woke up I recalled the previous night and felt the intense fear again though this time it lasted only around 3 minutes.