Are you using the Windows 10 default Balanced Power Profile? If so, make sure the Performance and Energy slider is set to Best Energy Savings. This will help reduce processor sensitivity to applications that request the maximum boost state from the CPU.
What cooling solution are you using and is it functioning correctly and is it correctly installed?
What is your case airflow like?
In the meantime you can try a selective start-up which can you help diagnose applications which are making calls to the CPU causing it to increase boost frequency, which raises voltage and temperature.
To reboot in a selective startup:
Press WINDOWS-R on the keyboard to bring up the Run window, enter MSCONFIG and click OK.
Under the General tab, click "Normal startup" if it is not selected already.
Under the Services tab, put a check on "Hide All Microsoft Services" and then click "Disable All."
Under the Startup tab, these will still be disabled in Windows 10 in the Task Manager.
Click OK on the MSCONFIG window, and then click Restart when prompted.