Inertia is not a process, but rather a fundamental property of all masses, being that they will continue in their previous state of unaccelerated motion, unless acted on by an unbalanced force.
Many badly written sites and textbooks ask the student multiple choice questions : "Which Object has more inertia : a), b) c) or d)."
That is a horrible mistake, Inertia is a property, not quantifiable. It is like giving two squares with different length sides. Which square's sides are more equal? Rubbish. They are really getting Inertia confused with the related but different concept of momentum, which is another topic.