I have a website designed and is live around eight months now. Four months ago it ranked on page 1 position 5 and it suddenly dropped to page 2 position 5 for three months with no changes to the website design. And now in the last month the website has gradually climbed back up to it's page 1 postion 4 without any website file change... What would ye think would be the reason for that???
If it was a few years ago, we'd call it Google Dance/sand boxing
Most likely it was your own search patterns - it sounds like detected personalised-search-while-signed-out. Even though you're a random user to Google to you, when you search for specific patterns you mostly likely follow the same action (i.e. scroll to see your site in the same place, don't click on anyone else etc). This is very easy to pick up. But nobody talks about it
Sites in low competition ranking spots don't just randomly rise and fall in a mathematically engineered system without a reason. If your income relies on it, you need a management plan. Don't mind the fluffers who want to be SEO's but really don't have a clue