Sounds like acid reflux. I had this really bad with my second pregnancy, so bad I had to sleep propped up because it would continually keep coming up. Definitely talk to your doc about it. Don't drink too much before going to sleep, and if you do drink something, take little sips. I have noticed if I drink too much water at once, this happens. Grapefruit juice is a good acid neutralizer. Drinking a small glass usually calms this feeling. Tums can work when it's not too severe as well. Try one of these before going to bed and see if it helps.
I agree if you have heartburn or acid reflux it can cause this. I'd definitely talk to your doctor about it.
Are you having bad heartburn the only time that has happened to me if if I have heartburn but I would mention this to your midwife doc etc because so far your lucky having woken up n not chocking on it