Perhaps he caught a draft or something? Also, I've heard as hedgies age, some need it to be warmer than it used to be. Another possibility has to do with the amount of light your hedgie gets. Even though he might be hiding under something during the day, he'll still need a good ~12 hours of light to help ward off a hibernation attempt.
Either way, since he's cold now and was wobbling, you'll need to keep the temperature higher than it has been in the past to keep him from trying to hibernate again. A heating pad can help if he's right on top of it in his cage, but he'll also need to be warm while eating, drinking, and running about. Do you have something to help keep the whole area warmer?