This article contains a issue which i had been experiencing for a long time. When encoder delay 15 seconds before each render no matter either it is a long clip or only a few seconds long. After some research i didn't find any solution, so here is mine.
Media Encoder CC - Edit - Preferences - Media - Turn off the check box Enable accelerated Intel h264 decoding
For those who have this feature withing theirs Intel processors may use this, but if someone as i am have an old Intel processors (Intel i5 Sandy bridge) may experience the same problem