Do you stutter less when you're by yourself?

Do you stutter less when you're by yourself? I was wondering, why is it that when I'm by myself I stutter significantly less? Like when I order food at a drive thru i'll stutter, but as soon as I drive off and repeat the order to myself i'll say it completely fluent. Doesn't this imply that stuttering is a psychological problem? Most articles that I've read say that stuttering is a neurological problem which i'm sure it's probably true (at least for me) since my brother also stutters like me. It must be in my genes. But what trip's me out is that I don't stutter when completely by myself. Even when I don't feel nervous I'll still stutter in front of people. Like wtf this just doesn't make sense to me! Or maybe i'm subconsciously nervous? Idk this is really bugging me though. I need help :(