Why won’t my TV display the PS4 Screen when you login?

I play a lot of games on my PS4, such as Plague INC., Just shapes and beats, minecraft and WipeOut: Omega Collection. But recently, I turned on my PS4, and it would start booting up, with the usual blue-to-white lights on the PS4, and the DualShock 4 with the flickering lights before it turns blue! But, display wouldn’t appear. I don’t have an HDMI OUT Cable inserted, but if I did, I did not notice it. I think maybe I need to insert a cable in?