Why Is It Sometimes I Shut Down Verbally? There Are

Why is it sometimes I shut down verbally? There are periods of time, for as little as ten minutes or as long as a day, sometimes with cause, sometimes without, in which I simply do not want to speak or hear my own voice at all. I have had depression, anxiety, and bipolar for several years, and I have been an introvert my whole life. I am not sure what to attribute this particular symptom to, and I would very much appreciate any insight and guidance.