This message was posted on behalf of Intel Corporation
In regard to your concern, this issue is related to overheating.
I would like to know if you have a Thermal Pad and it has been placed correctly? I have found a link, where you will be able to see more details about the Thermal Pad:
How To Fix Intel NUC Overheating Problem
Also at the following thread, you will be able to find the solution that was provided to someone who reports the issue with the same Intel® NUC Kit NUC6i5SYH.
Please let me know how it goes in order to further assist you if required.