4 mornings a week at 3:30am-ish my dog will wake up and vomit 2 or three times, before going back to sleep. This has been going on for a month now.

The vomit is usually just stomach acid, very pale and foamy. Sometimes, however, it is grainy, yellow and oily. No more then a half cup total of vomit, ever.

She's a young dog, a chocolate Labrador, 9 months old.

As such, she is /always/ watched. No potential garbage, plant or toy ingestion.

She's been on the same food (Solid Gold Hund-and-Flocken-Adult) for six months before this with no similar symptoms.

We give her 1.5 cups in the morning at 7 am, 1 cup at noon and 1.5 cups right before (her) bedtime at 7pm.

She is at a healthy weight, and is proportionate for her size and age.

She is completely up to date on all shots, and has been spayed.

Her poo looks solid and she's been going as often as usual.

She does not appear to be in pain, or lethargic or depressed. Her appetite is EXCELLENT (she is a stomach on 4 legs, aka LAB.)

Is this normal? Does anyone else have a lab/dog that has experienced these symptoms? Worth a vet trip, or am I overreacting?