New built machine, novice builder, and I need some guidance on system crashes.

ASUS Rampage V Ext BIOS 1801
i7 5930k
GTX 970
16gb running at 2666
Windows 10 Pro

System boost just fine and runs perfectly when in use, if it is left for around 4 or 5 minutes with no use it crashes, no blue screen, no error message no screen saver, lock screen or shut down screen.

Speedstep power management is set to enabled in BIOS, turbo mode is set to off.
All other BIOS settings are set to auto.

My thoughts are that power management to CPU is in error, BIOS settings not correct for CPU..
Can someone suggest where I look next, are there steps I need to take to fix power management of CPU?

Event log picks up the following critical error

Log Name: System
Source: Microsoft-Windows-Kernel-Power
Date: 28/12/2015 13:12:22
Event ID: 41
Task Category: (63)
Level: Critical
Keywords: (70368744177664),(2)
User: SYSTEM
Computer: DDDDDDD
Description:
The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.
Event Xml:



41
3
1
63
0
0x8000400000000002

5637


System
FourB



0
0x0
0x0
0x0
0x0
0
0
0





Thanks in advance folks, all help and suggestions appreciated.