My dog occasionally gags/vomits after drinking water. Cause for concern?

For the past couple of weeks my dog will start to act like he’s going to vomit/vomit a little after drinking water. He does NOT do this every time, but it has happened when he’s drank both a small or large amount. He’s never done it (to my knowledge) after eating. He’s acting completely normal so I don’t think there’s anything seriously wrong, but this new habit is worrying me a bit. I’ve had it suggested to me that it might be the heat affecting him, but I’m not sure. Thoughts?