I Have Had Three Blackout Incidences In The Last Two

I have had three blackout incidences in the last two weeks where I can feel myself start to 'go dark' and then literally see black. In all incidences I have grabbed on to someone so I haven't fallen. I come back and I am shaking uncontrollably. I have also noticed that my hands are shaking on a regular basis. I have a doctor appointment on Tuesday but am wondering what kind of research can I do now.