My 4 year old keeps getting fever every few weeks, mainly at night for a time spam of 5-6 days, what could be wrong with her? is this cause of concern

Hard to say, ? fever: The average 4 yo will have 5-7 respiratory and 2-3 diarrheal infections per year, most of which are minor and self heal.Kids also vary in their temp with lower in the early am and higher in the afternoon.(97-99.5) this could be an issue worth studying and a visit with basic lab could rule out the worrisome causes. I doubt major problems, but you doc should check to be sure.