I had this sensation since ever, for as long as I can recall. When I wake up or am sleepy and I stretch or yawn, I get this sensation in my head, mostly the top and forehead, like an electrical discharge but not quite. It's kind like if there was a low thunder inside my head, the "sound" it makes resembles a distant, damp thunder sound.
Now, I figured it was just a common thing everybody felt while yawning, except it started happening in "clusters", like one after the other non stop for 30, 40 seconds while I was falling asleep, and if I tried sleeping again after it ended it started all over.
And today it was especially disturbing. I was reading on the couch and started feeling really sleepy, like I had to close my eyes right then, so I did, and they were heavy as if I had been sleeping already. After like, 15 minutes, it started. After the first one I was a little confused, but still so sleepy I closed my eyes again, and then it got crazy, it started way louder and with high pitching sounds like those cartoon witches when they fly, coming in waves.

The closest I found to this sensation was the anti-depressant withdrawal syndrome referred as "brain shock". And indeed, I took 2 medications for panic syndrome 4 years ago, one which was an SSRI.
But as I said, I've had them all my life.

So... any thoughts at all on the matter, I'll take it.