I’m pretty sure you just made yourself pass out.
When cleaning, a deep breath and valsalva is good for the initial part of the lift, but you should let your breath just do what it’s going to do when you get to the explosive part. And you should definitely let yourself breathe after you rack the clean, before you press or jerk. I’m not at all surprised that you passed out if you made it a point to hold your breath through the entire thing.
Trembling and twitching (AKA spazzinesss) often accompany fainting. And when you faint, you lose consciousness. Not being able to remember what happened while you were unconscious/semiconscious is normal.
As long as you pretty much fully recovered and felt totally normal shortly afterwards (with the exception maybe of feeling a little tired) and didn’t, like, hit your head on anything when you were spazzing, you should be fine. Just don’t do that to yourself again--a gym has lots of hard surfaces and sharp edges, and you don’t want to be fainting in a place like that.
I am not laughing at you. I swear. Maybe Sully will chime in, as he knows syncope. But I’m fairly sure he’ll tell you that you just found out what it feels like to faint.