This screenshots says it all. It's the Google Search Console graph for the average position this year. The Average Position keeps dipping and recovering to normal. - Is this normal? - How can i stabilise this? - Anybody else with the same problem? Average Position 2018: Average CTR 2018: Total Clicks 2018: Total Impressions 2018: Combined:
Some fluctuations in both rankings and traffic are mostly a normal thing. Make sure your pages don't compete with each other, and the on-page is done correctly. Can't say much without further details.