My 3 yr old cat woke up this morning on my bed and started meowing. She tried to get up and just flopped over. She tried over and over again, but couldn't stand up. She pulled herself to the middle of the bed. Then I looked at her eyes and they were huge and it looked like she was chasing a fly in the air but there was nothing there. This went on for about 30 minutes and all of a sudden she was fine, jumped off the bed and went to eat. What happened to my cat?

It sounds like a seizure. Which is a symptom, not a diagnosis. To find out what might be causing it, you really need to see a vet.