Is there an underlying problem associated with excessive daytime sleepiness?

Yes: Excessive daytime sleepiness (eds) is not normal. It can be due to work schedule, medical problems, restless leg syndrome, psychological (stress/anxiety), sleep apnea or a circadian rhythm disorder. Best to be checked by a sleep specialist.

Multiple possibilty: Items on differential include: 1) insufficient sleep 2) sleep apnea 3) narcolepsy 4) idiopathic hypersomnia 5) thyroid/endocrine issues 6) depression this list is by no means exhaustive, but it's a good start. You should see your doctor to get a better idea of what may be going on.