Could sexual intercourse/orgasm while laying in bed (on your side) cause a brain aneurysm?

An aneurism is a weakened area in a blood vessel wall that exists and likely has been there for years. The cause can be elusive but heredity has been linked as one origin. Events that trigger a rise in blood pressure may lead it to break, no matter what that event. The cited position is not as important as the rise in blood pressure that any orgasmic event could produce.

A congenital berry aneurysm by description and definition has been present lifelong. A secondary rupture due to straining and valsalva-like activities can occur in any position

A body position does not cause brain aneurysm. Rise in blood pressure from any cause, including orgasm could contribute to rupture of an aneurysm.