This message was posted on behalf of Intel Corporation
You could try to run a BIOS recovery for this type of issues, the recovery file will try to fix any issue at BIOS level.
Instructions for BIOS recovery available below:
Were you able to run the BIOS recovery?
Thanks for following up on this one.
The problem was actually faulty RAM. I had 2 8 GB sticks in, and when I removed one the problem disappeared.
Amazon replaced the memory and now works a treat.