Sue
I used to suffer with this very badly, particularly at night, when I'd wake up and actually think I was going to be sick.
GP thought that it was probably diet, so I cut out eating just before bed. I also don't eat much white bread, and I've cut down my red wine intake (although I do still drink some). Also, rather bizarrly for a farmer, I avoid dairy products. Seems much better now.
The other thing that my GP mentioned was that this sometimes goes hand in hand with a heartbeat irregularity - so he sent me for an ecg - which was normal. Nonetheless it might be worth checking with GP.