I am not a doctor and do not know the difference between brain zaps and EHS (or whether there is one), but this article[1] summarizes it well.

For me, it is a loud sound but sort of within the head, accompanied by the sensation you get when you receive an electrical shock, which of course startles you awake. This unfortunately occurs just at the boundary between consciousness and sleep, which after it happens a few times in a row can put you off the idea of even trying to sleep. Occasionally I did awaken thinking there had been a literal explosion in the building.

I haven't taken SSRIs for 3 years and still get them, albeit less than when I was weaning off of them.

[1] https://www.medicalnewstoday.com/articles/brain-zaps#how-the...