Hello and hope you are doing well.
You could be getting inadequate sleep at night, which could be causing the daytime sleepiness. This could be due a sleep disorder. These disorders can be like obstructive sleep apnea, wherein during sleep there is an obstruction to air flow due to laxity of the throat muscles during sleep and this could cause restlessness. Hence for therapy CPAP (continuous positive airway pressure) is used to keep it patent. Another cause could be an entity called restless leg syndrome, where there is an odd sensation in the legs during sleep causing the individual to move, which relieves the sensation. These disorders can cause inadequate sleep leading to fatigue and daytime sleepiness.
Also excessive sleepiness is the symptom of a sleep disorder called Narcolepsy. This sleep disorder is characterized by excessive day time sleepiness, sleep paralysis, cataplexy where the person has episodes of loss of muscle function while awake, hypnogogic hallucinations and automatic behavior.
You will need to consult your primary care physician, who may schedule you for a polysomnogram (sleep test) to rule out sleep disorders and initiate appropriate therapy.
Hope this helped and do keep us posted.