I stutter when I'm around people but don't at all when im alone... i'm confused

I stutter when I'm around people but don't at all when im alone... i'm confused Ive had a stutter since I could talk and its been really had to do deal with in a social setting. However I have also been so confused as to why I only stutter when Im around people. For example I was at a university expo and it requires me to go around and talk to and ask questions about universities in general and what i may like to study. I go up to one of the boots and I am struggling to speak fluently and at the start of every sentence I just get stuck. But when I walked away after the struggling conversation I just had I tried to repeat it to myself outload and I repeated with no stutters what so ever. This will happen with anything, if I having a normal conversation with anyone I find it difficult to speak. But once no one is infront of me I find it extremely easy. I really don't understand why, as im writing this at home right now I can say any word or sentence on the planet without stuttering but when you put a person infront of me it appears. I am just writing this as Im curious if anyone has the same thing or with anyone has an explanation on why this is(Also I not nervous per say when I talk to people however knowing I have a stutter makes me nervous when entering a conversation, if that makes sense).