My dog keeps gulping and stretching his neck (suspect acid reflux). Has anyone experienced this?

Hi everyone, I'm looking for some advice and experiences regarding my dog's behavior (he's an almost 5-year-old Shih Tzu), while I wait to call the vet tomorrow morning.

This is an issue that has been coming and going for a few years, but lately, it had almost disappeared. However, it came back about a week ago. Basically, he has these episodes where:

He stretches his neck forward and continuously swallows hard/gulps.

He makes weird mouth movements, like smacking his lips, as if he's trying to get something down, has a sore throat, or is experiencing severe nausea.

Sometimes, in the past, he would throw up white foam or yellow liquid (bile) in the morning on an empty stomach.

He's not the kind of dog that eats random garbage off the street. Last week this discomfort lasted for a whole day (maybe he swallowed a hair after getting a trim around his face), then it went away. Tonight, instead, it started out of nowhere around 11:15 PM, several hours after dinner.

Doing some research, the symptoms seem to point to acid reflux or bilious vomiting syndrome due to an empty stomach.

Has anyone had similar experiences with their dog? How did you manage the situation (smaller and more frequent meals, a bedtime snack, antacids/gastroprotectants)?

Thanks in advance to anyone willing to share their experience!