How high has your temperature been running?
Is it then normal for the rest of the day?
There are a couple of options. It would be helpful if you could take your temperature with a thermometer when you feel feverish. Some people feel hot and have a normal temperature, or it could be a low-grade fever, or a more substantial fever. There are conditions that can cause a hot sensation in the mouth without a fever being present. There can be a burning sensation in the mouth related to acid reflux, which can get worse at night when you are lying down, so therefore most noticeable in the morning. There also can be inflammatory conditions in the mouth or a condition in which there is a burning sensation in the mouth, called burning mouth syndrome. If you are having a substantial fever, the primary concern is that you could have an infection. It would require an appropriate medical evaluation to determine the exact cause. If you have a normal temperature and only the burning sensation, most of the conditions are not worrisome, but should be evaluated and treated to help relieve the symptoms. If you are having a substantial fever, that is more worrisome and should be evaluated more quickly.