Hello, You will need to evaluate your sinus area. Post nasal drip can cause a very acidic oral environment and symptoms such as you are describing. You may breath through your mouth at night. This dries out the plaque and causes a coating on your tongue. Increase your oral hygiene as this type of plaque is very sticky and difficult to remove. Maintain good daily oral care and keep up with routine dental exams. Stay hydrated. Balanced vitamins are important for overall health as well. Avoid habits such as smoking that may cause oral irritation. Consider using a humidifier at night if this is a nighttime occurrence and you are not congested during the day. Reduction of salvia can accompany sinus congestion. A burning sensation with a coating on the tongue can indicate an imbalance of bacteria. Taking a probiotic can help maintain balance. A fungal infection such as thrush can require treatment with the prescription Nystatin. If the condition persists, visit a ENT specialist to determine if there is a sinus condition or a digestive specialist to look into a contributing gastric disorder. Thank you for your inquiry. I hope that my suggestions are helpful and offer you a solution.