I have never been cold due to low carb, but have felt cold due to not having enough sleep, or having been sedentary, or feeling under the weather, or change of season, or TOM, or stress/worries, or being thinner. I always take a sweater when I go to stores. The AC is too cold in the stores for me.
One hundred carbs per day is lower than the Standard American Diet, but it is not low enough for one's body to change the way it metabolizes macronutrients.
If you've stopped eating sugar or caffeine in the last few days, it might be the detox.
That's all I can think of, at the moment. Hope some of it helps.