ubuntu 16.04 LTS 64bit - screen goes black every 15 seconds

I am completely at a loss. On a new installation of Ubuntu 16.04 LTS 64bit my laptop screen has started to go black every 15 seconds. If I move the mouse or click then the display returns (I do not have to log in). Because this happens every 15 seconds the laptop is essentially unusable. It looks like screensaver behaviour but it could be anything.

If I type sudo lshw -C video | grep product: I get -

product: Broadwell-U Integrated Graphics
product: GM108M [GeForce 940M]

If I type sudo lshw -C video I get -

  *-display
       description: VGA compatible controller
       product: Broadwell-U Integrated Graphics
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 09
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:44 memory:f0000000-f0ffffff memory:e0000000-efffffff ioport:4000(size=64)
  *-display UNCLAIMED
       description: 3D controller
       product: GM108M [GeForce 940M]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:08:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress cap_list
       configuration: latency=0
       resources: memory:f1000000-f1ffffff memory:c0000000-cfffffff memory:d0000000-d1ffffff ioport:3000(size=128)

If I type xset s off this seems to have no effect.

If I type gnome screensaver I get -

** (gnome-screensaver:5014): WARNING **: screensaver already running in this session

If I type xscreensaver I get -

The program 'xscreensaver' is currently not installed. You can install it by typing: sudo apt install xscreensaver

If I type xset -q I get -

Keyboard Control:
  auto repeat:  on    key click percent:  0    LED mask:  00000000
  XKB indicators:
    00: Caps Lock:   off    01: Num Lock:    off    02: Scroll Lock: off
    03: Compose:     off    04: Kana:        off    05: Sleep:       off
    06: Suspend:     off    07: Mute:        off    08: Misc:        off
    09: Mail:        off    10: Charging:    off    11: Shift Lock:  off
    12: Group 2:     off    13: Mouse Keys:  off
  auto repeat delay:  500    repeat rate:  33
  auto repeating keys:  00ffffffdffffbbf
                        fadfffefffedffff
                        9fffffffffffffff
                        fff7ffffffffffff
  bell percent:  50    bell pitch:  400    bell duration:  100
Pointer Control:
  acceleration:  5/1    threshold:  5
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  0    cycle:  0
Colors:
  default colormap:  0x22    BlackPixel:  0x0    WhitePixel:  0xffffff
Font Path:
  /usr/share/fonts/X11/misc,/usr/share/fonts/X11/Type1,built-ins
DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Enabled
  Monitor is On

Needless to stay if I go to Settings > System Settings... and make changes to Brightness and Lock, Power or Screen Display this has no effect on the problem. I don't know what to do. Any help would be appreciated.

I have solved this issue. I have no idea why the problem was triggered. I don't know what the problem actually was. I don't know why or how my solution works.

I guessed that the problem was arising because of Display Power Management Signalling, or DPMS. I guessed that DPMS had been turned on by something I'd installed and that it was operating at a default setting of 15 seconds. I guessed that DPMS was turning off the display through the X server after 15 seconds (a default value) of zero activity in order to "manage power". I opened a console and typed

xset -dpms

This turns off DPMS permanently, not just for the session. The problem promptly went away.