It would be handy if you can get checked for deficiencies. When I was severely vitamin D deficient, I was also calcium deficient and I was falling asleep at my desk at work. So definitely get your vitamin levels checked. (don't just take supplements without things being checked as some supplements can make other things happen if you take too much). Anemeia can also cause fatigue so they can check that while you're at it. Someone has already mentioned the blood sugar spike and crashing... it's not that you can't have sugar but it needs to be small and in control. If your'e having carbs have it with protein as well as the protein will slow down the carb processing which helps with the spiking. But in all honesty, despite getting these under control, I still have fatigue and brain fog. I just no longer fall asleep randomly when I don't want to. I think it's the mental works we do of trying to manage everything... I find for this meditations, yoga or just walking in nature can help me. It's taking a timeout from the every day management and getting out of your head a little. it's not easy to start with as you feel you're fighting your fatigue to do it, but as you persist with the walks or meditation or yoga, you find over time it does help.

So get yourself checked for deficiencies, control your carbs and work on finding time for meditations, yoga or walking in nature.

if your fatigue comes from insulin resistance it could be your blood sugar is spiking then crashing try to cut down on simple carbs try more complex carbs and meals eith high protein and fiber to help with that cycle i also take metformin to help but it could also be a vitamin deficiency or other things so it depends on the person