I Am A 55 Year Old Female In Good Physical

I am a 55 year old female in good physical shape, exercise 4 to 5 times a week and weigh 135 pounds. 2 times in the last week I have had a sudden onset of generalized weakness and tingling with extreme feeling of light headedness. It comes in waves and may last several hours. It is not precipitated by any change in position and is not alleviated by eating or drinking water. It is not after I exercise-very random. Today just walking across a room and lasted several hours and abated quite a bit but feelings still there slightly with some tingling and heaviness in my arms. I took melatonin to sleep last night and take St Johns wort as well as MSM and tumeric for sore joints. I had not taken the tumeric or MSM last week as thought maybe there is some sort of interaction that caused these symptoms.