Once upon a time is said once, at the beginning of a story. Okay, so it says "the following is a little or longer story". But what does e.g. "um" several times

Once upon a time is said once, at the beginning of a story. Okay, so it says "the following is a little or longer story". But what does e.g. "um" several times per sentence say? "I should slow down but I don't wanna"? Even there being nothing inherently bad about them, they're by the same token also not inherently good, though I agree that the example in question is a bad one for a bad one.