I tend to have the same experience. After sex (excuse the example, just something I have recently been thinking), I tend to actually not stutter at all. When I have had a few drinks I speak much more fluently as well. And I attribute that to social anxiety, or the lack of it. I don’t think I started stuttering because of social anxiety though, but instead the other way around. Social anxiety increases my stuttering though, which makes me stutter more, which leads to more anxiety and so on. An evil spiral so to say.