Fever is a reaction of the immune system as it responds to (what it perceives to be) a threat. Beyond that, it could mean a lot of things. People with autoimmune diseases can get fevers frequently. I've been diagnosed with long covid and ME/CFS, and that's one of my symptoms. A friend of mine has rheumatoid arthritis and gets fevers, too. It'd be a good idea to make a note of when you have a fever and what other symptoms you have at the same time. It can help you see patterns and help your doctor find an answer!