Morning selfie describes the situation when someone posts a selfie to any social media in the morning, looking like he/she just woke up, but in fact, they already took a shower and put on make-up before taking the selfie. Still, there are someone stupid enough giving many likes to such kind of selfies.
Originallly, morning selfie means that you grab your phone and take a picture of yourself the moment you wake up. Then you post the picture to social media. The rule is you are not allowed to fix your hair, put on make-up, turn on the lights, or even remove the crusty stuff from your eyes.