I think it is:
I am faster than you can run,
Your skeleton runs at the same speed as you, but can do other things (like ride in a car)... also the same speed as you, but faster than you can run (since you too ride in a car faster than you can run).
so abandon me, go home and have fun.
A lot of people call the afterlife their true home and a happy place. If you abandon your skeleton, that's where you will go.
I live where the moon rise from above,
so abandon me, get rid of the hands in glove.
Your hands are the glove here. Your skeleton's hands are in the 'gloves' of your skin-hands.
I am soft like a kitty and hard like a rock,
Your skin is soft but your skeleton is hard.
without any warning we come in flock.
Not sure, but people do come in 'flocks' sometimes. Also in horror movies a bunch of skeletons might fall on you without warning or something. Also a graveyard is a 'flock' of skeletons.
Who am I that you might ask?
a symbol of fear, hidden in a mask!
Similar to the gloves one. A skeleton is a symbol of fear, and it's hidden in the 'mask' of your body.