Hello

I've had the phone for a few months now, so here's what I can say:
The device got warm quickly in the last few weeks, yes, but that was mainly due to the outside temperatures of a good 30 degrees, as every device gets warm. At "normal" temperatures, I only notice the warming at maximum screen brightness. (I always have Bluetooth, mobile data and location on).
In your case, it might be because you have an app with a short refresh interval, e.g. Facebook (running constantly in the background).

Here is the XDA thread about it: https://forum.xda-developers.com/lg-g6...
And an app that might help a little: https://play.google.com/store...