What Could Be Causing Recurrent 24-hour Episodes Of Sudden Fever, Chills, Weakness, Headache, And Loss Of Appetite?

I am 72 years old but don t look it. I don t take any presciption drugs except a muscle relaxer and an anihistimine on occasion. In the last couple of months I have had 4 episodes of sudden fever,chills, weakness, a mild headache, loss of appetite and today I had all those symptoms including dizziness. The episodes last about 24 hours and then I am myself again. I called my internist and he told me to come in the next time it happened. He also ordered blood work - not sure exactly what was ordered but I was told the blood work was okay. When episode 3 happened a couple of weeks ago I called him and told him it was happening and he could not see me for a couple of days. I told the nurse that the episode would be over by then and there would be nothing to see. So, I had episode #4 today. I would like to know what my next step should be.