Severe stutter when I'm not interested in a conversation!! Is anyone in the same situation?

Severe stutter when I'm not interested in a conversation!! Is anyone in the same situation? For example early in the morning when I'm sleepy and I get a call or when I'm too tired to talk to anyone or maybe even when talking to a person I'm not interested in talking to,I stutter moderately to severely.In other cases when I hardly stutter i.e I might not be completely fluent but I am okay.But I can never talk properly when I'm disinterested!