David Otunga says he flew into "flight or fight mode" when he encountered the dude who broke into his car Monday night -- telling TMZ Sports, "I'm ready to tear this guy's head off."
Little backstory ... Otunga had finished a shoulder workout at his gym in Chicago when he saw a man inside of his car trying to steal his stuff, including Apple AirPods.
The WWE star says he freaked out at first, wondering if the guy had a gun -- but quickly realized the burglar was a coward who immediately began to beg Otunga to let him go.