Whats the case of this? Anything he could do to stop this happening?

I think he might just be experiencing what I go through. Vivid all night long terrors except mine have a twist to them. Ask him if at any time in his life if he thinks about something, anything and a topic in life arises within it in a short period of time. If his answer is yes, I think I might be able to help. (Dreams are strage things! My dad talks Arabic, Spanish , German, English and Dutch in his dreams!) Maybe you should question his dreams and ask him if he can try to recall any! Tey may have underlying messages!