I’ve heard of lots of people first noticing tinnitus while being sick, as well as like the sibling comment, right after getting a vaccine (flu, covid, etc.) It seems like inflammation generally makes the symptoms worse, and I’d bet that most of the time inflammation is causing latent existing tinnitus to cross a threshold and become noticeable and reach your consciousness. I distinctly remember that the first time I consciously noticed my tinnitus, I knew I’d actually been hearing the sound very quietly for some time and not recognizing what it was… I don’t know how long I had tinnitus before I knew I had tinnitus.