My laptop dell wasn't able to open in just one press of the ON

My laptop dell inspiron 3421 wasn't able to open after shutting it down. You have to keep on onning on the ON and OFF button over and over again until it works..But sometimes there was a time clicking the ON button for the first time it turned ON at an instant. But when my laptop was already ON there was no problem at all I can used it all day long. I don't understand can somebody please help me.. Thanks in advance! God Bless U!