Sometimes when I get sick I can sense that it might happen when I go to sleep. I think it’s mainly about being the right amount of tired, though.

The other key element is having enough brain activity to keep your eyes open or to reopen them while your body tries to start REM sleep. People say stress will do that, and that tracks with my experience.

Also, try sleeping on your back. I’ve never had it while sleeping in any other position. It could vary from person to person, so maybe try sleeping in different positions.