Worried about extremely deep sleep. What could this be?

20F I am writing this because my sleep issues have started to significantly impact my safety and daily life. I would greatly appreciate any medical insight on what steps or tests I should pursue.
Main Symptoms:
• Extreme sleep depth: I sleep 8 to 10 hours a night. However, I am completely deaf to my environment while sleeping. Alarms have to ring for 1.5 to 2 hours straight for me to wake up. Family members struggle heavily to wake me up manually.
• Automated behaviors & amnesia: Sometimes, a phone call does wake me up. I answer it, have a conversation, hang up, and immediately fall back asleep. Later, I have absolute amnesia—I remember waking up to the ring, but I have zero recollection of what I said or that the conversation even took place.
• Sudden daytime sleep attacks: Even after a full night's sleep, if I sit down or lie down for just a moment to rest during the day, I fall asleep instantly without even realizing it. Once, I fell asleep in a very crowded, extremely loud bus. I didn't feel physically tired before getting on, but I just blacked out into sleep.
• Excessive daytime sleep: Recently, after sleeping a full night, I sat down, fell asleep, and slept for an additional 5 hours straight during the day.
Current Lifestyle & Context:
• I am currently unemployed, so I do not have a strict daily work schedule.
• I do not experience heavy physical exertion or high physical workloads.
• Subjectively, I don't feel like I am "deprived of sleep" or exhausted when I am awake, but my brain seems to just forcefully shut down.
This feels much deeper than just being a "heavy sleeper." Could this be Idiopathic Hypersomnia, Narcolepsy, or a severe parasomnia? What specific diagnostic tests (like a PSG or MSLT) should I request from a neurologist or sleep specialist?
Thank you for your time