This is a recipe I use to dip Marshmallows in that is soft and remains soft. I would think before you dip the pretzels in chocolate you would need to get the pretzels cool as the caramel is soft. Hope this help.

Melt together:
1/2 cup butter
1/2 of a 14 oz. can Eagle Brand or any condensed milk (not evaporated milk)
1 bag of caramels, unwrapped