So, for the first time I had a case of hypnagogic imagery. I was doing a relaxing technique, and was almost unconscious when suddenly I like, gasped for breath. At the same time, someone in my head laughed hysterically. It wasn't an evil laugh, and it wasn't scary. It just startled me, and I bolted upright.

I tried going back to sleep, but was unable to achieve it again. Does this happen often?