I had a similar issue but could narrow it down to when a USB-C dock was connected. If I connected the dock the CPU Usage and fan noise would increase after a minute or 2. If I disconnected the dock the CPU usage and fan noise would return to normal. Changing a BIOS setting fixed the issue for me.
This is the page that ran through the BIOS setting to change
http://itwalkthroughs.com/knowledge-...ock-connected/