The enable causes the voltage to jump. And like a mechanical jump this causes some moving, sone oscillations.
It is like when you pull on a guitar string. The pulling makes no sound, and if you slowly move it back to its initial position there is no sound, too. But when you pull, and release it, the the string moves and this creates a sound with decreasing amplitude.
In my circuit there are two feedback and one forward path. Due to multipole compensation some poles causing that oscillations even though PM is good. I did compensation again to change the position of pole. Now there is no oscillations if i give pulse.
We always concentrate on Phase margin but I learnt how gain margin can also affect the stability.