I haven't, but I also started out slow. Try lowering your dosage until you tolerate it better, or wait for a little altogether (listen to your body!)
Are you making sure to have organic acv? Apples are literally the most pesticide ridden of all the fruits and vegetables; if its not organic you could be reacting to the pesticides inside it.
Acv is most beneficial with the mother, as it is probiotic.
Also cold mean you have high stomach acid, in which case you might look for ways to lower it naturally.
It might be die off, but it also might not be. See if taking vitamin c helps :)