display flickers for nearly 30 mins after each start.

[yuvraj-here]

i have recently installed a ubuntu 18.04 on my pc. at the time of installation the monitor was different and now i have changed the monitor. initially the system and monitor was working fine but after i changed the monitor, the display started flickering. the intensity of flicker is high upon the start of pc and reduces gradually and after around 30 minutes of pc being used, the flicker gets reduced. also sometimes the app windows goes black, the main desktop page still works. i am very new to ubuntu as well as computers.please help.

[Autodave]

The first thing that I would do would be to try the monitor on another computer. That will tell you whether it is the monitor or your machine. Start there and report back.

[Impavidus]

Background light of the LCD, or maybe the plug isn't properly connected. What type of plug is it?

When the monitor gets to normal operating temperature, the flicker stops.