Simple 2D motion around a circle is laggy in Android.

This is my first time on Unity so sorry for all the noobness.

I am making a simple 2D game in which an object (call it M) keeps running around a circle, with simple obstacles(call it B) in its path.
Thats pretty much it.

I do not use any gravity.

Have added a Rigid body on M.
And have added box2d colliders both on M and B. Both the colliders are triggers.

I have made M go around the circle using the RotateAround method of unity.

The issue is that, the motion of M around the circle is very laggy in android.
And this is not a phone issue, as this lags even on good phones like the nexus 5.

I have read quite a few of the threads on lags on android, have tried to implement those fixes.
Still not much improvement.

There are just 4 images in total, and all of them are part of one png file, and have used the unity slicer to create separate sprites.
Any inputs?
I wouldn’t mind sharing code as well.

Make sure that anything which affects a rigidbody (such as rigidbody.AddForce(…)) is in the FixedUpdate() function. This function is called right after, or during (not sure) the physics update!