(I haven't worked with this physics in decades, my terminology might be off)
First year varsity physics: Inertia is a property of mass. It is the amount of force to start an object moving (or change a moving object). The more mass the more the force requires, in direct relation.
Mechanically speaking, how does inertia work?
The force isn't absorbed, accumulating or converter. The result is that there is an equal but opposite force pushing back - as long as the force is equal or below the inertia threshold. What gives mass have this property?
Does weak, strong interaction (Nuclear Force) or quantum physics feature? (1kg of contained gas has the same inertia as 1 kg of lead. Thus the state or density of matter doesn't matter)
PS: Can it be a property of space-time to resist the movement of matter? (Sounds too much like friction...)