That is so weird, my 2 yr old daughter is going thru the exact same thing, she has a fever and i give her acetaminophen and it goes down but then as soon as the meds wear off it is back. Don't really know what is going on, she is just groggy and not really eating a whole lot but not throwing up or any other signs of illness.
A fever is usually the response to a viral infection sometimes a bacterial one .,a fever is the sign of an underlying cold or infection.A temperature itself is rarely dangerous,if it continues with out any other symptoms it is always a good idea to have her checked out by your doctor.