You actually have asked several questions, so I’m going to try to answer them. Your first example does sound like stuttering, but the 2nd one doesn’t. Stuttering is not common; it affects 1% of the population worldwide. People who stutter know what they want say, the just struggle to say it. The common forms are repetitions (re-re-repetitions), prolongations (prrrrrolongations) and (silence…) blocks. No sound comes out when you are stuck in a block. Excitement, anxiety and other emotions can make stuttering worse, but they don’t cause it. Hope this helps!