She vacillates between clarity and intense confusion. Is there something that triggers it?

It might be helpful to consider the health conditions and medications your mom normally takes. Low blood pressure can cause temporary confusion. Please talk to your mom's doctor about these episodes since they may point to an underlying disease process or be warning signs of an impending stroke.

likewinered: Imho, perhaps she should be seen by her primary care physician for starters.

There are types of dementia where this is the pattern of behaviour especially in earlier days. There is as has been suggested the possibility of TIAs. Perhaps a visit to a neurologist would be useful. Personally I don't see UTI as an issue, that doesn't come and go from day to day, although it can cause considerable confusion. It sounds more like a neurological issue than anything else - quite possibly one that will deteriorate and nothing can be done for, but an exam and any necessary scans would help you understand the current and likely developing situation.

Just enjoy her clear moments! Eventually they will show up less and less.

My mom got like this after her second jab. Her good days are nice, the rest of the time, not so much.

likewinered, think of your Mom's brain this way .... imagine it is a video tape that goes around and around on a spool .... parts of that tape are clear and parts of that tape are foggy.

If the fogginess tends to happen more so in the evening, then that is called "Sundowning". Or does the fogginess happens just before eating or after eating? Have a notepad handy to write down what you notice. Then look for a pattern.

I know for myself and my sig-other [we are both 75] that we tend to be tongue-tided at breakfast time. It's like our brain is still half-asleep.

My mother has had a history of TIAs (mini-strokes) and epileptic seizures. These can definitely affect the continuum between lucidity and being confused.

Has she been seen by a neurologist?

UTIs in the elderly can cause all kinds of symptoms that clear once the infection has cleared.

Another possibility is that she's having TIAs, sometimes called "mini-strokes".

When was the last time she had a comprehensive exam by her PCP with you present to report symptoms?