I bet it's due to a deficiency in some trace nutrient that covid depleted you of and you simply haven't recovered it somehow. that would explain why it's such a specific pattern, there's a slight mechanical issue with your memory system

I read somewhere that covid depletes your system of choline and other B vitamins, so I got these https://jarrow.com/products/neuro-optimizer-120-capsules and it seemed to help with my brain fog at the time, and make a quick recovery after it passed