I read your question carefully and I understand your concern. That description could have several explanations like dehydration and electrolyte abnormalities, transitory disturbance of heart rhythm, thyroid dysfunction, orthostatic hypotension etc, it is difficult to point a precise cause with that information alone. At times when the episode is isolated and transitory no cause is identified even after physical exam and extensive testing. So what is recommended especially if the episode repeats is a heart assessment and some routine blood tests like blood count, blood sugar, liver and kidney function tests, thyroid function, electrolytes, vitamin B12 level. I hope to have been of help.