I believe your issue is caused by software on your system not compatible with the Windows 10 operating system this software is causing memory leaks.
The software is more than likely your antivirus software as this is mostly used from boot up. Your best option is to start task manager by pressing CTRL, ALT - DEL together and selecting it from the list, See what applications are running in the background then close them down see what kills the fan speed. You can also click on performance tab then resource monitor from within the box you'll see what software or programs showing high usage you should be able to work out what software is the issue then seek an update for that software. The problem with updating your operating system then older software often needs updating too.
First thing i would do is do not connect to internet is your fan still running high then disable your antivirus software completely reboot then see if you fan is still running high it's a process of elimination with other software.