There are a number of things that can give you spells of being sort of in another reality. Like dissociation, derealization, abnormal brain waves (epilepsy), an underlying illness etc.

After I had strep I started to sort of zone in, like my head was thinking really hard and trying to grasp things to the point I was no longer here and now. Very weird feeling. But it sort of passed with time. I know strep triggered it but I don't know exactly what it was.