Excessive daytime sleepiness can be a cardinal sign of Obstructive Sleep Apnoea (OSA). If you snore, wake feeling as though you've been gasping, or have a partner who notices pauses in your breathing, please speak with your GP.
The Epworth Sleepiness Scale (ESS) is a clinically validated tool for assessing sleepiness objectively. A score over 10 is worth discussing with your doctor.