I was hopeing to get a response back from you before answering. The behavior or your puppy seems to be neurological in nature. This might be indicative of a disease that attacks the nervous system such as distemper, or may be symptoms of seizure activity which can occur when a dog is small and for one reason or another doesn't eat. You can read more on distemper below and hypoglycemia (low blood sugar).
Another cause for a dog to be looking around suddenly and jerking like you describe could be an issue with the eyes though I would suspect a corneal ulceration. An ulceration can leave a spot on the eye and the dog sees it just barely and keeps moving their head in order to try and see it clearer but since it is a spot on the eye, no amoutn of moving the head allows them to see it easier. This can make a dog a little anxious as well. An ulceration can be from scratching the eye or a branch from a bush hitting the eye or even from an eyelash. Some breeds can also be prone to retinal detachment as well. Read more on that here.
At her age, I'd have your vet take a quick look and ensure her vaccinations are up to date.
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