Weird iPhone 11 Issues. Board Problem?

So recently my iPhone 11 has been acting a little weird. Here’s some background info…

Back in February or January, I had my phone on the car mount with the heat on (I can’t use a CD mount since I don’t have a CD player, so I use a vent mount). One day, it overheated the phone and I didn’t notice until I got to my destination. Previously, my phone did have the occasional issue of refusing to connect to the stereo (it would show the loading wheel in settings and wouldn’t do anything), and this was the only way to fix it:

1. Turn off BT (this would usually take like 3 seconds)
2. The BT slider would gray out for about a second, but then you could turn it back on.
3. You could then reconnect manually by selecting the stereo in device list.

Neither my 5S or XCover Pro do this, so it’s likely a phone issue not a stereo issue.

After the overheating incident, everything has gotten worse. Whenever I use my hotspot, my phone will randomly turn it off and disconnect, and sometimes it just acts VERY slow. Also, the Bluetooth issue from before has gotten worse and sometimes I have to reboot my phone to fix it. It’s also disabled itself a few times.

Also, after this incident, my phone will occasionally shut off when it’s dropped. Some applications also act up and slow down occasionally, but it’s not too bad.

Is this a board/hardware issue or a software/iOS issue?