Odd when you develop bad anxiety issues from seeing a stress induced seizure...Afraid you will have one from stress when its what stresses you?

It's a trauma. Observing someone go through a seizure or other painful events can result in trauma or even ptsd for the observer of the event. Generally the fear passes and does not leave a lasting mark. If it persisted treatment with a therapist skilled in treating trauma and phobias should be considered.
Acute stress DO? If u r too much bothered about it talk with u pcp for treatment.