There's a setting I saw on Instagram about this where it will send you emails if you're inactive for too long. It's an entirely distinct setting from all other email spam. There was one setting on Instagram I would toggle, and come back two seconds later to find it retoggled, it was to suggest my account to other people to follow, I've managed to acquire like 20 follow requests from total strangers, I can't make it stop.

Something is seriously wrong with IG. I'm a programmer, this is the sorta thing if I heard from someone else I wouldn't believe, but it's fundamentally broken imho.