My almost 3year old daughter has recurring high fever (104.5) every few weeks or so with no other symtopms., last for 4-7 days. Dr has no answer?

Peds rheumatologist. The most likely cause of recurring fever in children is infection. Kids in daycare for the first time will often get repeated viral infections. If she has already seen a pediatric infectious disease specialist and no likely infection found, your next stop should be a pediatric rheumatologist. We specialize in autoimmune and autoinflammatory disease diagnosis and treatment: pfapa, fmf, traps, etc.
ID consult. Has she been evaluated by a pediatric infectious disease specialist?
Genetic? A host of genetic semi-diseases, from cyclic neutropenia to familial mediterranean fever, can do this. I would consider asking for specialist referral. Your child is fortunate to have a parent who is so devoted as to seek advice from strangers. Good luck.