Fading mental is a minimum equivalent of blocking: thought engulfs for a few moments. (Wikipedia)
In clearer (if I understood correctly what I was told) the patient starts a sentence, slows down his speech and does not end his sentence, then resumes on another sentence.
With friends, when I spoke during these periods where I was surely worse than usual, I had the impression, when I said a sentence that what I was saying was stupid, null, uninteresting, that people would end up finding it frankly stupid if I continued, then turning the gaze elsewhere, this impression was very strong and I was ashamed, so by an uncontrollable reflex, so strong was my gene to say a silly thing, I gradually stopped my sentence telling myself that I had done well to stop it before the end because it would have been silly to go to the end, the others having certainly already understood what I wanted to say and already found it uninteresting. In fact I didn't realize that others surely didn't understand what I meant at all and might find it strange.
Also surely at these moments, my mind filled with constantly flowing ideas had trouble understanding what others understood from what I was saying at the moment I said it, I had trouble visualizing what others must have understood with my words, often I had the impression that they had enough elements to understand where I wanted to go, while surely not, I realized that I was misunderstood, but I could not express myself to be well understood.
And then I also had frequent memory lapses, my mind invaded by ideas, making me think one thing and then another, and then I forgot the first thing I had thought of. So much so that my word was hard or impossible to follow.
I think if you are psychiatrists and ask your patient why he has this fading, he will not give you my explanation, because he may be embarrassed to reveal that he is ashamed of his sentences, that is what I would have done at those times. Also because his mind confused in a thousand worried ideas, impressions, he can have a lot of trouble understanding what drives him to do this.
On the other hand, if you put a patient several months later, when he is much better, facing this fading, I think he may be able to tell you that yes, he stopped his sentences gradually because he was ashamed to finish them, if he remembers this moment.
I'm not completely sure that others feel this way during their fading, but I have this memory of not finishing my sentences because I was ashamed to finish them during these periods.