Three problems that I have heard of:
If it sounds normal and the battery is the original white Varta or old it is probably the battery.
If it sounds a little off like it is a "dying cricket" then it may be the alarm siren - only way to keep it quiet is to leave it unlocked until you replace it. Buy from Mercedes not Chrysler - #'s on the forum.
Also a problem with water in the trunk getting the locking module wet. Instructions available without removing the foam.
Do a search and you should be able to get the info you need on the forum. A good start is: https://www.crossfireforum.org/forum...ht=alarm+siren