2010 Subaru Forester clunk sound when I start driving

I have had this car for about 3 weeks now. After I put the car into drive and drive usually around 5 feet, I hear and can feel in my feet a clunk under the car. I looked in the manual and it says that you may feel some vibration when the car automatically tests the anti lock brake system. I don't know if this is the clunk that it is talking about since it happenes after I have already backed up, shifted to drive and have already driven a few feet. If anyone knows I would appreciate it.