Waking up from a coma is common. I personally know one lady, with whom I was undergoing therapy at the hospital, who had been in a coma for three months and then “woke up”. When I asked her what it was like, it seems to me that she said it was like a very long deep sleep with no consciousness of the passage of time.
I was in a coma for 3 weeks from an unintentional poisoning. A diocese priest even rushed to the hospital and preformed Last Rights for me. I don’t remember waking up, but I heard I was very angry and violent and had to be restrained to my bed. I don’t remember any of it, and don’t really even remember leaving the hospital. A strange experience in every way.