What Causes Loss Of Balance In Body?

Hello, I am a 73 year old man who works out at the "Y" most days and still work.

I had a "spell" at the "Y" when after exertion, I got light headed. Had an Echocardiogram, Ultra sound to my Carotids, and some blood work. All normal. Yeaaaa!!

Now yesterday I got out of my vehicle to do some work and was losing my equilibrium.... bad!! I got my work done but with great effort not to fall down. I would totter off diseways for 3 or 4 steps before recovering. I thought of calling 911 but it subsided after 30 minutes maybe and I drove home very slowly.

Can you shed any light on this for me??

Thank you.

R.K.N.