Dell E173FPb 17" TFT LCD Monitor "picture goes until warms" Questions

...picture, which would last till I turned it off again. Yesterday, when I turned it on, it started displaying weird lines and malfunctioning, as well as only showing for two seconds and dissapearing ...

...picture comes on for 15 seconds and it goes off till I swith on again or unplug the VGA and plug in again, it does the same. Time for staying on becomes less as I continue the exercise Hi, It sounds ...