I 100% can tell when I’m going to stutter. Usually I can word switch around it (which is why I’m perceived as more fluent than I am), but I intimately know the sensation and the kinds of sounds / situations that cause it. I also think there’s a “don’t think of a purple elephant” effect to stuttering. I know mine gets worse when I’m stressed, so the stress of feeling like you’re going to stutter could definitely fulfill that prophecy.