If you run a tidy ship, you could go through the apps you might suspect, there is a "set an alarm" permission under settings -> apps -> app -> permissions -> three dots -> all permissions.
I don't think stopping / clearing app data makes it go away if it's do persistent, so you might have to resort uninstalling the apps that have this permission until it goes away.
Our cat has a craving for chocolate, milk and everything not good for her.
She's not the brightest bulb