Hello, I am an Audiologist.
Pretty much everyone experiences that random, fleeting ringing from time-to-time, which is why the old wives’ tale came into being. Unless you have other symptoms associated with it, it is probably nothing.
We do not actually know the mechansim for tinnitus… whether it is happening sporadically, as you describe; or chronically, as @pjanaway and I experience.
Tinnitus is a vague symptom – like a headache – that might be isolated and benign or could be caused by something more serious. Different types of sounds are reported by different patients. The pitch of the sound often correlates with the frequencies where the person’s hearing is the poorest. But many people, including myself, have tinnitus with normal hearing.