Thats probably bad filter capacitors in the power supply .. the chinese made capacitors are going bad at a high rate .. you can usually identify the bad ones because the normally flat top becomes bulged upward ... replacing the capacitors will often fix the problem .. you have to be brave enough to disassemble and do some soldering .. the replacement caps are not expensive ..

Check for any magnetic fields if not check the power cable for any voltage fluctuation..or else you may need to change the monitor...