I would definitely recommend going to see a doctor who specializes in sleep medicine, preferably one that is American Academy of Sleep Medicine
board certified. Based solely on the limited amount of information you provided, it is difficult to say what the problem might be. Possible diagnoses I would consider would be Hypersomnia (i.e, excessive daytime sleepiness), Idiopathic Hypersomnolence (i.e., excessive daytime sleepiness due to unknown reasons), Narcolepsy.