Hey there! I know many people who have used Citrine, a stone of energy and light, to help summon energy and keep them generally energised, it's also a very pure stone so it never really needs to be cleansed! Just wear it on you during the day.
I have sometimes used Garnet for energy and it is rather effective, but in this case I think Citrine comes out on top.
Of course gemstones can't cure all so try and get a good night sleep also! :)
What you are experiencing is drowsiness or even fatigue, which can be caused by several problems. Anemia, life choices like a night shift, anxiety, boredom, stress, depression, diabetes, low sodium levels, sleep disorders like apnea, vitamin B12 and iron deficiencies, certain medication. The list is endless. Run some tests, visit a doctor and do what he tells you to do. And you can boost the doctor's therapy by picking a gem to target the cause of your problem.