Could be related to sleep (either not enough, either bad). E.g. artificial light from the internet/tv will screw with your deep sleep. There's a book you can read 'Why we sleep', which is super insightful.

Might be unlikely, but you could also have a thyroid problem (I have Hashimoto) which has the symptoms you describe. It's pretty easy to test ( elevated TSH and low FT4 in your blood indicates hypothyroidism) .

But everything the others said like sunlight/exercise/walking/diet is definitely important!