Hello Laura, as @strongevergreen mentioned, the feeling can be caused by the body concentrating its energies on digestion. In fact, it even has a name "postprandial nap" - in some societies it is considered normal. Perhaps yours is happening because your body has less energy to spread around while trying to heal from Covid. I also noticed your profile says you also have chronic migraines. Do you take any medication for it? Many meds are known to cause sleepiness, and that may be complicating matters.

One coping suggestion - when I was working, had 2 small children and was constantly sleep-deprived, I often had that feeling at work when I ate even a moderate lunch. I found eating all protein, veggies and a small amount of fruit made me less sleepy than a sandwich or anything with carbs. I eventually avoided all sugar during the workday, and added a half cup of coffee at lunch as well.

Other strategies that can help include staying well-hydrated (helps digestion) and a short walk after eating to help circulation (even just a stroll around the yard.)

I hope you can find an answer that works for you.
Sue