Why is the secondary monitor turning on and off randomly

I have installed an external monitor (samaung) connected to on my laptop (asus gl552). I am using a HDMI cable for connection. Since the laptop does not have a vga port, I have connected a HDMI to VGA connector on the laptop end and inserted the cable in HDMI port of the laptop..

I have switched off the laptop display and adjusted the screen resolution on the samsung external monitor to 1920 x 1080 and adjusted colors for the Windows 10 and brightness and contrast from the monitor.

The problem is the monitor turns of blank intermittently for 1-2 seconds and turns on again at random interval. What could be the reason for this and how to get rid of this problem?

Please I need help. Again how can I configure the Nvidia card to be used by the external monitor not the in-built intel grapghics 530

Thanks in advance.

Note: The video I inserted is one I found on the net. but That is exactly how mine is behaving. Instead I quickly uploaded it for you to see.