Typically it is the first start of the day that produces the noise (in the period that it occurs if so) and then you usually don't get it again unless you let the car sit for a few hours or so.
An oil AND filter change usually gets rid of the issue for most cases for at least 10,000km. If you are experiencing the rattle way more often than that and well under 10,000km since your last oil and filter change, your VVT-i controller is definitely playing up.
It is not normal for this to occur on cars with VVT-i. They are meant to have a functioning locking pin in there to prevent this from happening.
Just to confirm, this is the type of noise you are getting right? I had to use another example because Murphy's Law states that all times I've tried to film my car doing it, I could never get it to happen (actually I've never heard it since I started using Penrite SIN 0, even after 15,000km):