Welcome to the Q&A Forum

Brand new pages can fluctuate in rankings for a while before they seem to "settle", yes, but for some queries, results are different day in, day out. There is no set time period for a new page to "find its place". Google seems to sometimes test whether new resources "deserve" good rankings: the page may seem high-quality - if Google ranks it well for a short period, does the page attract traffic? Does that traffic stay on the site? Do people bounce back to the SERP and choose another resource? Does the page attract links? Social media attention? A page may drop down in rankings for a time, rising again as its attracts more links. There is really no good rule to go by, besides understanding that a brand new page with good rankings may not have great rankings forever, and that SEO work is still required to keep its rankings high.