Working with sugar isn't easy, and it requires a myriad of ideal conditions to operate well, including how it's stored to the order in which ingredients are added.
Caramel sauce is made using butter, salt, cream, water, and sugar, but it can get tricky getting the sugar component right as it can easily get burned or grainy in caramel sauce.
To ensure its silky mouthfeel and smooth, sweet taste, warm the cream before adding it to the caramel sauce, as cold cream can lower the temperature of the sugar and crystallize it.
Cold cream added straight to the warm sugar can also make sugar granules jump to the side of the pan, where the sugar is likely to crystallize away from the moisture.