Which medication/s are you taking?
Some of the more common reasons for tiredness are:
(1) The blood glucose roller coaster
(2) Vitamin or mineral deficiencies, especially D3, B12, folate, magnesium, potassium, sodium
(3) Thyroid issues
though I'm sure there are others.
Before diagnosis, I would regularly need to go back to bed after eating a breakfast that spiked my blood glucose. I also had a Vitamin D3 deficiency at the time.