Whenever I enter my car, bluetooth is connected. What I would like is my speedcam alert application to be started once BT is connected and ideally terminate application when disconnected. I am using LG G6 with Nougat.
For such automation purposes, you can use any one of the following-
Takser is somewhat difficult to use and paid app so I will recommend you to use IFTTT or Automate. IFTTT has supports for a variety of products such as Phillips Hue lights etc. But Automate is the easiest to use for your purpose.
In addition to the answer by Deepak Gangwar, might I also suggest MacroDroid? Among other things I use it to change the in-call volume whenever I connect my BT headset. With BT it detects the specific device paired, so it can do different things for e.g. BT headset or car. It comes as both free and paid app. The free versions has a limit to how many macros you can define (I'm not sure about the exact limit, but it is quite low), but is otherwise fully functional.
I'm not in any way affiliated with ArloSoft. Just a happy MacroDroid user.