My SO has been having a terrible time trying to sleep lately. Usually something like nightmares, or he's waking up constantly. He just can't get a restful sleep and I don't know what I can suggest to help.

He is physically active, going to the gym 6/7 days, works mornings, walks to work too. It is summer weather here and the poor guy just can't cool down very well so part of it may be the heat? Got any suggestions that might help him sleep? And no, I don't live with him. O only stay over for a night every other week ish.