My dog is usually standing. Is focused on the ground. His body is waving back and forth. His stomach muscles are contracting. Like he is going to vomit but doesn't. When he snaps out of it. Be has problems walking like he is dizzy. Then he is fine after a couple of minutes. Whole episode lasts about 5 mins. Has happened 3 times in the last month. Eating fine. No accidents. No vomiting. 7 year old. Just changed food? Will make a vet appointment but wondered if there are any thoughts. Thanks