I have CFS/ME. Its completely normal for me to fall 'asleep' anywhere and everywhere, at any time of the day. As long as I am comfortable.....
Conferences, cinemas, trains, buses, car journeys, at the beach with the kids are just a few of the places.
However my weirdest one pre-CFS was probably my bosses sofa. He (and the rest of the office tbf) had noticed my performance had dipped and I wasn't my usual self. So he called me in for a chat, popped out to get some water and by the time he was back I was spark out.
What no-one knew was that I was still living at home but things were far, far from OK. It was a domestic violence household and I was pretty much scared to sleep for various reasons.