Three possibilities come to mind (and rest assured: cancer and HIV do not present as such):
1- Acid reflux: if you have acid from your stomach going up into your esophagus and throat, you will feel soreness in your throat, usually accompanied by heartburn or acid brash, bitter sensation over the back of your tongue, sometimes with mild nausea; these symptoms are common in the morning since the stomach is empty, the acid secretion is high, and you've been lying on your back which facilitates the reflux process
2- Post-nasal drip: if you have nasal secretions or sinus secretions that go backward into your throat (what we call post nasal drip), this causes throat irritation, vocal cord swelling, and hoarseness
3- Mouth breathing/snoring: nasal blockage or any other cause of obstruction in the airways (including obesity) force you to breathe through your mouth. As a result, your throat gets exposed to air all night and dries up, hence the soreness.
Of course you need to be evaluated by a doctor to find out the exact cause and treat it accordingly.