Same here, mine definitely is a result of social anxiety though. I have a near to perfect home life as such, and have lots of great friends at school so it's weird I have the social anxiety to begin with - but I definitely know it's there. For example I'll literally just be in a conversation, and my scentence will just come out completely jumbled for no reason. Imagine saying "I saw a cat on the road" my words would come out something like "on the road uh I saw uh a cat on the road" or I'd just stutter on a word completely making me really confusing to speak to. It could be possibly starting school again even if there is no definite stress. Especially since its come out of nowhere in particular. Just my opinion though :)