clunck sound from trunk

[estle4]

I have a 01 sunfire,there is a loud clunk noise sounds like coming from trunk ,as i stop at a stop sign ,and then take off ,is when you hear the clunk,and feels like someone just hit me in the rear of the car, doesnt do it while i drive,took the spare out still does it., sounds like something hitting against something in the drunk,.any help appreciated.