I usually see it portrayed as getting stuck on a repetitive loop that's running away from you. That's not really how it feels for me. If I was trying to get someone to convincingly portray what I think I'm like when I stutter I'd say imagine you're repeatedly trying to push the word out of your face but something is blocking it. Sometimes you can't even push the first syllable or even any air out and you block. Sometimes you get a little bit out so keep trying again and again. But the harder you try and the harder you push the worse it is.