On my Mac, whenever I turn it on, the Bluetooth Setup Assistant automatically pops up. I always have my Bluetooth on, on my phone. Could that be why? Also, when I turn off the bluetooth on my phone, the Assistant doesn't go away. It only goes away if I unplug my mouse and plug it back in.
It keeps searching for bluetooth keyboard and mouse for some reason.
iMac is on Mojave (latest versions) My mouse is a Macally Mouse