This is in my personal life, but I know someone like that too. I know what you mean, it makes hard to think because every 5 seconds they just keep chiming in when you’re trying to figure something out that’s complex and they’re just saying random things. It got to the point where I’d basically just say “just give me a minute to think?”, or something like that. I don’t think the others here have met someone who talks like you’re describing, most people don’t talk in that way, its like an obsessive compulsive thing with them. My advice is just find a way to make it clear he needs to stop for a minute so you can get the job done better without being too rude. I think if you convey it that way he’ll understand better and not feel like you’re insulting him.