Is it normal for a Guinea pig to cough?

I would check the inside of his mouth and his cage for things that he should not be chewing on, or swallowing. Guinea pigs can not vomit at all, so hiccupping would be a sign of abnormal breathing, or a reaction to something in his mouth. Also does he have any other drainage in his lungs or anywhere else that accompanies the hiccups? Hiccups can be from Upper Respiratory Infections, because the drainage restricts normal breathing. If he has any plastic, or wooden toys that he has been chewing on, remove them, and see if that helps, he could be trying to eat material like that. Let me know if you have any more questions. Amber xx