I started getting these post-Covid, but I'm not on any SSRIs. It feels like your brain does a "degauss" thing like the old CRT monitors; it's not fun.
There's some evidence to show that long Covid is connected with low serum serotonin, and the zaps make me wonder if it's connected to cerebral serotonin as well, since I imagine it's the sudden reduction that causes the zaps: https://www.cell.com/cell/fulltext/S0092-8674(23)01034-6
Wow, now that's an interesting one! You described the feeling perfectly though, it's exactly like that. I wonder what would happen if you took an SSRI...