2004 Honda Accord car shakes at 2 1/2 RPM's

Shakes or Wobbles problem
2004 Honda Accord Automatic 143, 00 miles

I have a '04 Honda Accord. 3 times in the past week my car shakes and slows down when I get to 2 1/2 rpm's. I was hit from the back on the interstate last week and its done it 3 times since then. It hasn't done it before so I don't know if something was knocked loose. My engine light has been on for several months but ran fine. It shakes and slows down when I get to a certain speed or when I speed up. It don't do it all the time but it its getting more frequent. Could it be transmission problem? I do have 143,000 miles on it.