There’s no difference between “psychological” and “physical” These are made up words, all stutters occur due to you’re brain being a bit scuffed. Unless you’re talking about trauma induced stuttering which isn’t natural, it’s caused by well… trauma. “It’s all in you’re head” whilst usually said in a dismissive and mean manner. Is correct. We’re all different, and so different conditions will affect us all different with some conditions like nervousness being somewhat universal, and others like rehearsal being more specific. Your stutter coming and going like you described is just part of what makes you unique. What you’re describing to me… sounds like a moderate stutter only caused when feeling unusually high amount of stress and anxiety, which isn’t too abnormal, compared to us severe stuttering folk.