Monitor shuts down while cpu is working

Hello,
I'm having an issue with my desktop computer monitor. It shuts down while cpu is working and its signal lamp shows its on but it isnt. If i turn it off and on on the switch then it works again for a few seconds(minutes) and then again same issue. Also before it turns of its like white color on the screen turns a little darker. Can u help? Is it my motherboard, graphic card, monitor itself or monitor cable issue?