Just know getting used to vape juice is hard. I would buy things that were described as 'snickerdoodle cookie" and all I could taste was playdough.
Is it too telling that I actually know what that tastes like. Hahahah. Well, I know what it tasted like in the late 60s, not so sure about modern Playdoh though. I've had pina colada, and ceral killer (Cap'n Crunch With Crunchberries) that were super good for a few days then tasted like Playdoh as well. I'm thinking anything with mixed fruity/berry flavors go bad pretty quick...probably totally depending on the actual flavor/brand used? I've had better luck with RY4, caramel, vanilla, bakery type stuff.
Back on topic. Most e-juice will behave like that when first "mixed". The watery flavoring, nic concentrate, PG and VG (is thick!) will look like oil in water until you actually mix it well, and will look like a cloudy mess during mixing, until it "blends" into one, then becomes nice and clear again.
Now if you're talking about something that had already been well mixed then separates again when it sits...I have never seen that. Some oily flavoring in it or something? Does it mix up clear and smooth if you shake it a bit? I am referring to plain old e-juice too, not "salts". I have never used those.