What Causes Recurrent Fever?

I m a regular gym goer, yesterday as usual, I came from gym had my protein shake, and then had breakfast and lunch, after which i suddenly got into fever, which with help of crocin came down at night, then in morning again I felt feverish, but on checking the temperature, it came on to 96.8, after certain time again my body went cold and now I am feeling fever again.