Stuttering is like a shitty connection. Even when you think it's good, you never know where the video will block and start buffering. You can hide it, or slow it down by reducing the video quality, but sometimes it doesn't matter what you do and the video keeps buffering anyways. As for describing how a block feels, it's like having a boulder on your chest that makes speaking awfully hard and complicated for no reason whatsoever, and you can't do much about it. It's like speaking when you are out of breath, you can just press on and hope to get your words out.