Oh wow! Let's make sure we find this culprit then BigBadBill1961. Try going to Settings>Language & Input>turn off Voice cmd for apps and then select Text-to-speech Output and make sure Driving Mode is set to off.
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Which phone do you have? Knowing exactly which model with help narrow down the model specific instructions.
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Oh my! We want you to live, so let's get this fixed. Go to Apps ➔ Settings ➔ Accessibility and uncheck TalkBack. Keep me posted.
Sometimes on my dumb flip phone, (inadvertently) pressing the external speaker button while the phone is closed -- and all other buttons locked -- sometimes toggles driver mode.