K.D.
My oldest son (now 11 ) also did this when he was about 3. He would get so mad he would run into things, scream, he would also bang his head and run into the wall at full speed. (sometimes this would last for 30-45 minutes) My husband and I were at a lose, you never knew what would set him off. We took him to the doctor, they found nothing, we took him to a counsclor, that didn't help either.
What we found, was he was a really smart kid (He's a GT Kid) that was having a hard time communicating, and he got really frustrated because he couldn't explain what was going on. So we changed our wording, Like I bet your really mad right now. I know it's hard, but the calmer you are, it helps, We also became very consistant in our actions, when he was in trouble, he would be punished everytime, when he was good, always praise, how Good he is behaving. It took us about 2 months, of constant work. He finally got out of it. Ever so often. He would have to get a check on his anger. But he's 11 now, and a really great kid. So hang in there their is hope.