I'm having severe chills off & on with periods of hot sweats. I just returned from Florida where I was in the sun quite a bit, though not having any sunburn. I ran for 45 min this morning at a moderate pace and felt fine. On the plane coming back I experienced two hours of feeling freezing cold and shivering. Since I got off the plane, I'm still experiencing periods of cold and hot. Other than some fatigue and a mild fever (100.5) I feel fine. Should I take any action right now, besides just going to bed? I'm 63 and have been a runner for many years, though these days I just do moderate race walking.