I have a Benq monitor with the same problem, sometimes it starts turning off and on without touching it.
The issue is that they use an ADC pin in the microcontroller for all the buttons, using a resistive divider. With time, buttons become slightly conductive (in the order of kOhms), and this screws up the voltages read by the ADC, triggering spurious button presses. As wraper said, try disconnecting the button board to see if that's the problem.