It was slightly more gradual than your dad's case, but the actual dizziness came on rather suddenly. I had been having a slight bit of dizziness when I would go to bed at night, but I'm slightly anemic, and I figured I just hadn't been getting enough iron. I felt really drained, and spent a lot of time lying around, which I attributed to poor sleep for those couple of days. Then, while I was reading on the couch, I felt really dizzy all of a sudden and my heart started racing and I had chills. I felt very intense anxiety and had this unnatural sense of doom. It was rather disturbing.
I don't know which kind of labyrinthitis that I had. My doctor said that it was probably either viral or could have resulted from a calcium deposit forming. He gave me medication and also suggested that I lie with my head hanging off of a bed and turn my head slowly from side to side a few times. Apparently, people can sometimes develop calcium deposits that can rest on one of the tubes of the labyrinth, the force of gravity when you're upside down can knock them off. Then, it just has to take time to settle down in the fluid of your ear, afterward. I tried this, and felt REALLY dizzy immediately afterwards (I was walking as if I were on choppy seas), but then things started to improve rapidly. So, at this rate, it could have been either form.