Why is the position of the site on requests storming?

Question

Google

Hello.
The guys began to track the positions of the pages by request, we receive data daily.
Very often, pages fly out for a hundred, return to the top 30-40, fly out again, and this is repeated again and again. Google search.
Titles, descriptions, headings seem to be normal (changed a couple of weeks ago).
With what it can be connected? I will be glad to educational program and opinions.
Thanks in advance.
Changes in positions over the past few days