I am working on a website whose keyword ranking keep on fluctuating every 15-20 days. Sometimes it is on 1st page for 5-6 days, then it goes down for 15-20 days. The website is not new that the ranking keeps going up and down. This is something new that I am not able to understand.
Onpage changes might be the reason... Content update, title, description .... is it static or dynamic site (any e-commerce site)?
Google constantly adjust Rankings as these have specific algorithms which catch data from websites. If Google catches something positive, they will improve your ranking, if you made some bad changes OR other websites improved, you will be ranked worse. Hope it helped to understand it better.