One day I went into one of my Google Ad Accounts I was managing, and I noticed all sorts of changes made that I didn't do. I started to freak out a little bit, wondering who could be doing this.
I looked at the change history and sure enough, changes had been made to the account and to my surprise it wasn't an actual human that made the changes but Google itself.
This was quite shocking as I had never encountered that before and I've managed countless Google Ads Campaigns over the years.
I had to get to the bottom of this and find out how to turn this off!
After some Googling and clicking around in the account, I found this setting in the Account Settings:
You open that bad boy up and by default it's set to auto-apply recommendations. You have to check 'Don't automatically apply ad suggestions' if you don't want recommendations applied automatically.
I'm not sure why Google is pushing this now but I don't ever automatically adding any recommendation. You should run an Experiment to test any major adjustment like bid strategy and let the results of the Experiment decide if you stay with the new bid strategy.