My narcoleptic sleep attacks often ended with a harsh awakening. It was like being underwater and then suddenly breaking the plane of the surface. The light, the external pressure, the sounds changed. Everything was instantly different.
It was kind of like time travel. All of a sudden you're thrust into this unexpected and unknown environment. From a sound sleep. Having an anxiety attack.
I would wake up with my ears ringing, my heart pounding, and have to figure out what was going on around me.
Kind of like I feel right now.