What you are experiencing is called the freshness factor. Internally, Google refers to it as QDF (Query Deserves Freshness). To ensure that searchers can find fresh timely information, they will temporarily boost the rankings of fresh new content. After this temporary rankings boost wheres off, your page’s rank will sink to it’s truly earned ranking.
This is normal rankings fluctuation, all experienced SEO practitioners will come to expect such rankings shifts due to the freshness factor. It is not the Google dance, it is not the Sandbox, it is not anything except QDF, the temporary freshness factor boost.
As you create backlinks, in the form of new content, you are getting short term rankings to boost from that new content. To establish more permanent rankings you will need to continue to promote your content, and as it earns trust over time, your real rankings will improve.