Have you been to a gastroenterologist? You may need some gi testing done? Have you tried anything for this? Gas x? Etc? Maalox? Mylanta?

That can happen to me if I eat the "wrong" foods. I would suggest tracking your food choices. Some of what you eat may not digest well. The other component could be stress. Since it doesn't seem to be constant, I do not expect it is the configuration of your digestive tract.

You might want to be tested for SIBO (small intestine bacterial overgrowth).

I am on a feeding tube into my small intestine and pump fed for 10 year's now. I get sibo regularly. But causes me pain. I have to take antibiotics regularly. But it never causes gas and belching. You should see a gastroenterologist. I have many gastric diseases and it is best to catch them quickly or things can get worse really fast. Good luck.

Possible causes of belching: https://my.clevelandclinic.org/health/symptoms/belching
https://vagusnerve.com/the-role-of-the-vagus-nerve-in-burping/
Within the digestive system, the vagus nerve plays a crucial role in coordinating various processes, including burping. As food travels through the esophagus into the stomach, the vagus nerve senses the presence of gas and triggers the relaxation of the lower esophageal sphincter (LES), the muscle that separates the esophagus from the stomach. This relaxation allows the gas to escape in the form of a burp. Thus, the vagus nerve acts as a mediator between the stomach and the brain, facilitating the release of built-up gas.

Explore if you have something like SIBO, GERD, LPR, h. pylori. Also people with GERD sleep on an incline of 45 degrees. You could try that and see if it helps. Personally I sleep sitting up. Good luck!