Dear Aayush

Automobile engineering is a sub branch of mechanical engineering, though it is studied as main branch in some engineering colleges.

Difference according to study

In mechamical engineering you will learn every mechanical object or machines out there in the world. You will have more generalised subjects like theory of machines, dynamics and kinetics of machines. You will have machine oriented problems.

While in Automobile engineering you will learn Automobile IC engines, Vehicle Dynamics, Vehicle kinematics, etc

As I'm from Mechanical, I can say that it's better to choose Mechanical than automobile as per the opportunities too.
Comment here,  if you want more information.
All the very best.