While the science of physics has led to explanations for a lot of phenomena, there are things that have to be assumed as is in order to frame a theory at all.
To give context to what I want to say, let me discuss the concept of 'level of description'.
In physics a breakthrough moves the level of description to a deeper level.
Example: Kepler had formulated the three laws of planetary motion.
Newton moved the level of description to a deeper level, showing that when you grant the inverse square law of gravity, and $F=ma$, then Kepler's laws follow from that.
A recurring pattern is this: the physics community can never know whether the current level of description is the deepest possible. Generally when a deeper level of description comes it is unexpected. (Actually, because it has happened multiple times in the history of physics there is now an 'expect the unexpected' expectation.)
In retrospect we see that the ancient greek thinkers thought of motion in terms of friction. The expectation was that any motion, under any circumstances, will come to a stop, unless a continuous force is applied.
As we know: friction correlates with velocity. Roughly speaking friction is proportional to velocity.
It was through the efforts of Galileo Galilei and others that a notion of inertia was developed. As we know, inertia is independent of how fast an object is moving. Instead, inertia opposes change of velocity.
An analogy to inertia is available in the field of electromagnetism: inductance. If you have a coil with self-induction then you get the following property: upon change of voltage the current strength tends to change, but with a coil with self-induction we have that that change of current strength induces a magnetic field, and that magnetic field act counter to that very change of current strength. The stronger the self-induction, the stronger the opposition to change of current strength. Note that inductance is inherently responsive; in order for the opposition to arise there must be a rate of change of current strength to begin with.
Scientists always focus on problems that look to have a decent chance of being solvable. By contrast, let's say you are presented with some puzzle, but you are not given any clues. Then you won't try that puzzle. You can't make bricks without clay.
In the case of inertia: I believe you have not found resources because very, very few physicists allow themselves to wonder about the origin of inertia. There are no viable clues.
To my knowledge it is extremely rare in the physics commmunity to contemplate an attempt at formulating a quantum theory of inertia.
(I have seen proposals of a connection between inertia and the Unruh effect, but to the extent that such proposals get a response at all it is that they are qualified as are a dead end; the idea is regarded as untenable.)