It's sad that fictional shows create such high expectations of autopsies.
My Niece was found dead in bed, deceased at most a couple of days, probably less.
The Autopsy was unable to unable to establish a cause of death.
She was epileptic, depressed, and self-medicating for a painful back injury. It's conceivable she had a seizure and choked, or took too much medication, regurgitated and choked, or even that she overdosed accidentally or on purpose.
What makes it especially painful is that such deaths require a coronial inquest, that my brother and his wife felt obligated to sit through, and it provided no closure.