QtM has a pretty good list there!
Sleep clinic ho speaking from experience here.
Hypersomnia wouldn’t be diagnosed with just a regular nighttime sleep study, usually - I mean, with just a nighttime study, they’d let you “sleep” at night and send you on your way without ever knowing you fell asleep in the elevator on the way to your car.
If that were suspected, you’d probably have a daytime sleep latency test which involves much the same wiring as a nighttime study, but the way it works is they have you lie down for 20 minutes at a time, 4-5 times over the course of a day, and measure how long it takes you to fall asleep. If it’s less than a certain average (10 minutes? mine was 5 years ago so I’ve forgotten) you might have some degree of hypersomnia or narcolepsy.
Ideally such a test would be in conjunction with an overnight study - yeah, 24 hours in the place - but that way they can be sure you really got “enough” sleep the night before, and you’re not stressed and extra-alert because of the hassle of getting there during rush hour. I actually left a former sleep practice in part because the doctor ordered the daytime study, but not a confirming nighttime study as well.
kayT mentions have a friend diagnosed with Restless Legs Syndrome as part of a study - actually RLS is usually not diagnosed that way, the diagnosis relies more on patient reports. Because with RLS, you really don’t fall asleep. Periodic Limb Movement Disorder (PLMS or PLMD) is something that does show up on the sleep study. Someone with one very often has the other, however, so if you do have RLS, it’s worth getting a feel for the degree of accompanying PLMD.
All that said: if your frequent waking is an issue, you can certainly try behavioral modification as a low expense option and see what that does for you. I personally used to have a lot of trouble with waking for a bathroom break, then my mind would rev up and make it hard to fall back asleep. I manage that by using an iPod to play something my mind can half focus on instead of glomming onto whatever daily problems I’m dealing with.