My guess would lean toward allergies or acid reflux. Both can cause you to wake up with sore throats that fade once you are up for a while.
I would suggest that you try allergy proof bedding (matress, boxsprings, and pillow covers) and keeping your rooms as dust free as possible. If this doesn't help, try some of the acid reflux life style changes. You might want to start with those since they are cheaper.
Take care and feel better. Feel free to ask as many questions as you feel like you need to ask.
Hi, welcome to the forum, firstly source of sore throat should be ruled out. It may be a infection or it can be due to air pollutant or dry air. The commonest cause of sore throat is streptococcal infection. Send blood or throat swab for culture and antibiotic sensitivity. If associated with fever, then you need empirical treatment with a course of broad spectrum antibiotic against prescription.
Another possibility is environmental pollutant like dust particles, heavy metal fumes, smoke, mold, old AC and even dry air can cause sore throat or throat irritation. Firstly, drink adequate fluids esp. before sleeping. Avoid exposure to harmful fumes or particles. Take lozenges and honey which will help to reduce the throat irritation. I suggest you to consult physician. Take care and regards.