What are some ways to get a sense of euphoria naturally?

Many. It depends on what you enjoy personally, but some ways include: dancing, music, enjoying nature, holotropic breathwork (sometimes) and falling in love. Some seek euphoria through the use of psychedelic substances like mushrooms, lsd, etc -- and some indigenous people use similar things in ceremony. But these aren't necessarily "natural" to other cultures, and euphoria is not the goal either.