I have this happen too. My temp is usually around 98.6, but oftentimes, it is 99.3, which would be a similar spike to what yours goes up to. No doctor will even consider it an issue until you reach 100. I've asked several myself and they say that anxiety can do it, eating, being in a warm location, etc. I notice my face often feels on fire, but the temp is still under 100. I just have a fan on me and drink cool liquids to cool off, which normally works.