Is there a period of low ranking after indexing for the first time for every site ?

Hey!

I've recently published two websites, targeting very different keywords woth minor competition.

Both of these pages started between rank 90-100, despite being relevant to the keywords. I also cared a lot about On-Page SEO.

After two weeks, both pages shot up to rank 1-9, without any form of effort from my side.

So it seems to me, as if there is some kind of "test period", where the website is ranking really low on purpose. There are also hints towards this in blog posts, but there the timeframe way longer (up to 6 months)

What are your experiences with this ? Is this just normal behaviour I have to factor in (possibly with more time before ranking properly) with every website ?