I think paranoia, like you describe, is indeed a first sign. I can relate to your seemingly unreasonable suspicions. I had nearly the same about workmates at my old job, when very sick. Thinking, in general, becomes more and more disturbed and/or dysfunctional. For me, disinhibition and impulsivity can go from manic without psychosis to manic with. The psychosis seems to bring behavior that is even more irrational.

With psychosis, my speech is also often affected. Mild "word salad", disjointed thinking, repetitions, sometimes stuttering, and/or making odd noises or singing.