I think it's normal for people to get disoriented when speaking, especially if you're tired or you just don't feel like speaking clearly or thinking about something too hard. I've been stuttering since I was 5 years old (now 32) and to me it's like the words just won't come out, like something is holding your tongue. I know what I want to say. For example someone asks for your name and you just can't vocalize it no matter what (well maybe if you force it out). Of course stuttering comes in numerous forms but I think what I've described is a common symptom of stuttering, they're generally called "blocks". Another one that causes my stuttering is a word that starts with "W". If I'm speaking and I have to say a word my brain will usually preempt me and I'll stop mid-sentence. Repeating words is not really something I experience, except repeating the start of a word.