Trunk Lid problems of the 2003 Chrysler Concorde

At times, when the trunk is open and the trunk lid appears to be locked in the full-open position, it will silently slam shut. This has happened while I am leaning into the trunk. It has hit me hard on the back of my head three times, leaving bruises. It also hit my husband on the back of his head once. Because the trunk is so long, we have to lean in far to reach items, exposing our heads to the descending trunk lid. We are also worried that our three year old daughter who is eager to help out reaches into the trunk while we are loading / unloading the car and that she could get hurt. The lid landing on her head or arms would be crippling. The long trunk lid is heavy so it picks up a lot of speed and hits hard. It also does not help that the part of the trunk lid that hits is hard folded sheet metal (as opposed to the softer plastic housing for the latch). Usually, the trunk lid does stay up. This problem only happens when it's cold - and then sometimes immediately, sometimes after a few minutes.