Could this have been epilepsy?

Hi, please excuse my ignorance. I am medically uninformed.

There is this fellow who I’ve been hooking up with every couple weeks for the last few months. I just suck his dick for a while, that’s all we do.

Last night we went the longest we’ve gone, must have been idk over an hour of me giving him head and him kind of edging with my mouth, tongue, and throat.

The thing is, about halfway through, I started noticing him doing this sort of…quaking? Like his head was kinda shaking side to side, like how you do when you say, “no.” But it was clearly kinda involuntary, and it started mild but then got a little more noticeable and intense looking. So I quick asked, “are you good?” And he said, “yeah!” And didn’t elaborate and I didn’t ask.

What do you guys think this could be? He does poppers during this, which I doubt is the cause but idk cuz I don’t do them really. Also, as a side note, because I’m only sometimes looking up at him I can’t say for sure, but he might pour his poppers on a towel that he holds up to his face, or it’s something else on the towel, and if it’s something else maybe that’s what it is? Or is it epilepsy?