Even the Sistrix Update Radar issues a warning that the fluctuations could indicate a major update. For the SEO experts among you who are optimizing Europe-wide: Germany is a little quieter in a European comparison - in France, Italy, Spain and the United Kingdom something really wild is going on in the SERP. The Sistrix value for the SERP dynamics there is twice as high as in Germany, or even higher.
There is still no official statement from Google on the movements in traffic and rankings. Smaller updates basically happen on a daily basis: The rating and sorting of websites is continuously adjusted and optimized. Most of them don't even notice many changes, but they are the reason that a placement in the SERP is never set in stone and has to be checked regularly.