Keywords disappearing and appearing from Google - is this normal?

Hey guys, it's been a while since I've been back here. I took some time off building websites as I got myself a new job but I'm back building sites again.

Just so you know, I've previously built niche sites in the past and had success but I've been out the game a we while and I'm wondering why my keywords are disappearing and coming back.

I have a new website which is just over 2 months old with only 2 links as I've not started my link building campaign yet.

At the moment I'm focusing on High Quality Content. Heres the stats below:

Site age: 66 days old
Number of articles: 46
Length of articles: 1,200+ - All Unique
Backlinks 2 - 1 blog comment - 1 High PR Directory
Google Analytics details: 3,780 impressions and increasing over the last 28 days.
All keywords are longtail and very low competition.

I have a lot of keywords ranked on page 2,3,4,5 which I think is fantastic since the site is very new with no DA and I know from previous experience a lot of these keywords will be page 1 in a number of months but I'm not sure why some of my keywords/articles are disappearing and then reappearing again while other keywords/ articles are ranking better at times.

Is this the sandbox effect or something?

Thanks for all your help and advice in advanced.

Cheers