Passed out during sex?

My partner and I had a somewhat lengthy foreplay session, but as soon as the “main event” started, my vision started blacking over, my hearing went muffled and over the span of about 10-20 seconds of that happening, I passed out. It was only momentary and I was fine immediately afterwards. But I’ve genuinely NEVER had that happen.

The only time I’ve gotten a bit lightheaded would be when getting choked, but that wasn’t happening at that moment and I’ve never completely passed out during sex no matter what is being done.

Is this something that can just happen sometimes? Has anyone else experienced this? I was laying on my back, had no sudden change of position, etc.