I wouldn't rule out the pandemic being an issue here. These are not _normal_ times, and is an additional stressor. For me stress _definitely_ impacts my ability to think clearly, and the higher the stress (even if not immediately obvious to me), the worse my thinking skills are.
As another commenter mentioned, migraines can also do this. Not all migraines come with a lot of pain, so that's not always a dead giveaway. But during a migraine, my thoughts are muddy as hell.
Just seconding this by proxy. Thanks to some early steps, I'm about as unaffected by COVID-19 as a person can be. I live in a neighborhood with acres between houses, telework to an office across the country, and am not at all unused to not leaving the house for a week at a time. In addition, I was able to make a bigger-than-usual trip to Costco in addition to already having some disaster preparedness steps taken well before-hand (fresh batteries, fresh water containment, rice / flour / staple foods on hand, etc.) and yet I still find myself at numerous points throughout the day thinking about some things I need, or might need in the near future, trying to find ways to procure said thing without leaving the home, and it's draining me in very small doses.
As another commenter mentioned, migraines can also do this. Not all migraines come with a lot of pain, so that's not always a dead giveaway. But during a migraine, my thoughts are muddy as hell.