Hello~Yes, I have had this, it is awful. I, too, get very scared and feeling slightly dizzy afterwards. I have been told that this is due to anxiety and also tight muscles in your neck. When we sit at our computer, our head and neck are actually bent in an unnatural position, this in turn can sometimes cause these sensations, so can looking at your cell phone too long.
Normally, this feeling is due to taking certain anti-depressants and SSRI's, but chronic stress can definitely cause them as well. I don't take any meds and as I said, I have them.
Chronic stress. People who don't take psychotropic or sleep medications also experience brain zaps and head zaps. Chronic stress, which we call stress-response hyperstimulation, is a common denominator for those who experience head and brain zaps.