Fevers out of nowhere?

Hi, it is important to note I am awaiting diagnosis.

I have been suffering for around 3.5 weeks now with various neurological symptoms. For the past week or so, I have had random fevers which come on with blurred vision and migraines and then fade after a few hours. They make me feel exhausted and extremely sickly. Any idea why they come on at random? I haven’t been able to find any triggers.