I don't know about sex dreams but pilots and stewardesses have gotten into trouble for having sex in the cockpit.
Last flight i had (first class) went to use the lav and could hear 2 people going at it had to wait 15 mins to use it they got told off by the fight attendant was funny.
Nope and no . I’ve heard stories about people having sex on a plane before but personally I haven’t seen any stuff like that . Sleep walking isn’t probably hard for one you have a seat belt on and second it’s to cramped to move . In less you’re first class where there’s some space to to move