Due to long term sleep deprivation in night time or delay in
sleep will lead to excessive day time
sleep or sleepiness, which happens due to change in normal
sleep-wake cycle. This is termed as hypersomnia of central origin. If stress is present, you need to go for relaxation exercises.
You need to undergo tests like Polysomnography, Multiple Sleep Latency Test and CSF levels of Orexin/Hypocretin which help to substantiate the diagnosis.