Well you may not be paranoid after all!
As it turns out, there are a fair number of Apps that have been accessing the Bluetooth on your iPhone or iPad without your permission.
There are genuine reasons why Bluetooth would be needed for certain Apps. Maybe things like Spotify or other Media Apps that may connect to Bluetooth Ear Phones or Speakers for example. However there some Apps that should never need access. The more nefarious may want access to track your location.
So, how do you find out which Apps are accessing your Bluetooth? In a word..."Upgrade!". With the new iOS (13) Apple have introduced a new privacy feature which force Apps to ask for permission to access your Bluetooth. Just a note...the Apps themselves will not change with the upgrade to iOS 13, they will have always been accessing your Bluetooth. It's the iOS upgrade that now allows you to identify the offending Apps.
So, what happens after I upgrade to iOS 13?
Once you upgrade to iOS 13 and open an offending App, you will be presented with a pop-up asking for permission like below:
As you can see, this App has given explanation as to why access is needed. Other Apps will have a more generic reason:
It's entirely up to you on which Apps to allow but, as a general rule of thumb, I would select "Don't Allow" for every App that is requesting access and then if you find the functionality of any given App is diminished in anyway due to lack of Bluetooth access (Highly unlikely), you can then allow access later on.
Once you have denied access to an App or Apps, you can navigate to your settings to show the list of Apps which requested permission and their current permission status:
Select Settings > Privacy > Bluetooth
From here you can toggle on or off access to your Bluetooth for an App.
Of course, if you have already upgraded iOS 13 before reading this article, then at least you now know what those pop-ups meant and what to do with them going forward.