Well this is a holy shit moment for me. My grand mother was having really strange hallucinations, like explaining how she was talking to people on TV and the neighbours came round and joined in too. I had never heard about the infection thing before. It was really upsetting my mum and no health care professional ever suggested it might be infections. This was ten years ago and she's dead now, but I wish I'd known then.
It sounds very similar to your experience, they'd just randomly come and disappear after a while.
> no health care professional ever suggested it might be infections
Acutely altered mental status (without specific findings suggestive of a stroke) is, first and foremost, assumed to be a metabolic issue. I've been a practicing doctor for twenty years and it wasn't a new thought at the time. I don't know why nobody suggested it to you. It's been basic understanding for, well, ages.
Even more amazing, is one of our friends is a doctor (general practitioner) and she never suggested it. Though she did say old people tend to just develop dementia and it's probably that (my gran lived to 97). It's the coming and going nature of it that no one seemed to pay attention to.
It sounds very similar to your experience, they'd just randomly come and disappear after a while.