cl500 probs

I have a 2003 Cl 500 and my trunk seems to be going bad. When i try to open it with my keys or within the car the trunk starts to open normally than stop opening and you can hear the pump running. Same thing when trying to close it with the button. You can hear the motor running but it doesnt really begin to close. I have noticed the only to properly close it is to hold the button for a little then begin to guide it down manually. This is the only way it properly closes. When u just press the button to close it the trunk goes down and when it closes you can still hear the motor running for a while and the right corner of the trunk stays up. What does all this mean??? Please Help.