What Causes Nausea And Disorientation In A Healthy Female?

Hi, what would cause short periods of nausea and some disorientation in a fit female runner (runs 3 - 4 miles daily), 52 years old during a run? It happened Friday and again on Saturday, and I immediately stopped when the nausea began. After a few seconds it went away and I continued my run. The disorientation continued (not as prominent as during the nausea) the rest of the day. My husband noticed I was repeating myself some of the time. I did not exercise yesterday or today, during which I ve been clearheaded.