A bit scared

Several months ago, I had a few episodes of becoming momentarily disoriented while driving a very familiar route.  I spoke with a psychologist about it, and he said if it happened again to take note of what was taking place right before.  I don't recall anything significant preceding those events.  It didn't happen again until this past Saturday.  My husband and I were going to a wedding, and I was driving.  I came upon an intersection, and all of a sudden I did not recognize it at all, and I didn't know which way to go at the stop sign.  My husband guided me to make the correct turn. 

This has frightened me.  I never forgot what my destination was or the fact that I SHOULD have recognized these locales, but I could not for the life of me figure out where I was.  The episodes were very brief, lasting probably no longer than 10 seconds each.  Naturally, I'm afraid it might be a sign of early onset Alzheimer's.  The psychologist said it is not necessarily so and just might be a symptom of stress. 

I'm only 51, very active (exercise daily), relatively healthy, and in pretty good overall shape.  Has anyone else had this happen to them and it was just a temporary symptom of stress?  I'm praying to God that's all it is and would be grateful for your prayers as well.  Actually, I think I'm going to post this in the Health section, too.

Thanks.