God is immanent and transcendent at the same time, immanent as pervading everything and transcendent as its the cause and principle of everything?

Let me share Verse four and five from Chapter Nine
of
Bhagavad Gita first which may help in understanding the reply.

Lord Krishn sings:

“The whole world is pervaded by me, 
the unmanifest Supreme Being, 
and all beings dwell within my will but I am not in them.”

The unmanifest form in which Sri Krishn exists spreads through every atom of the universe and all beings have their life within him. But he is not in them because he exists in an unmanifest form.
Since accomplished sages are one with the unmanifest God, they discard their bodies and act in the same divine state.

And then:

“And even all beings are not within me, 
and such is the power of my yog-maya that my Spirit,
the creator and preserver of all beings, 
is not within them.”

Even all beings are not within Sri Krishn, because they are mortal and dependent on nature. But such is the greatness of his yog that although he creates and sustains all beings, his Spirit is not in them. I am in the form of the Self not within those beings.
This is the achievement of yog.

This is practical and this great gap that is being mortal in physical form dependent on nature and being in the form of Self which is immortal unmanifest state can be experienced
only in deep state of meditation at very higher level.

And now transcendent as its the cause and principle of everything.

As per Bhagavad Gita, there are the five principles that Sankhya acknowledges as accomplishers of all action.

The mind is supposed to be the doer.
Virtuous and evil inclinations are the agents.

Performance of righteous action demands a predisposition to discernment, non-attachment, tranquility  self-restraint, sacrifice, and constant meditation.

But lust, anger, infatuation, aversion, and avarice are the agents that effect unrighteous deeds.

There are then the manifold efforts-the endless desires-and the means. That aspiration begins to be fulfilled which is supported by means.

And last of all there is the fifth principle, providence or sanskar-the outcome of all that has happened to the Soul in the past.

These are the five causes of whatever action a man accomplishes with his mind, speech, and body,
either in accordance with or even in contravention of scripture.

Now adds Bhagavad Gita:

“Despite this, 
however he who-out of his immature judgement-
views the consummate, 
detached Self as the doer is dull-minded 
and he sees not.”

As the Soul is identical with God, the pronouncement also implies that God does not act.

Lord Krishn has said in Chapter Five that God neither acts himself nor impels others to act, nor does he bring about even the association of actions.

Then why do we say that everything is done by God? 

It is only because our minds are clouded by delusion. We just say whatever comes to our mind. However, as Sri Krishn has affirmed, there are five causes of action. Yet the ignorant man, incapable of perceiving the reality, views the lone, Godlike Soul as the doer.

He fails to realize that God does not perform any deed. Paradoxically, however, while saying all this,Sri Krishn also girds up his loins for Arjun and assures him that he has just to play the part of an instrument, for he (Krishn) is the real doer-arbiter.
What after all is the sage’s import?

In truth, there is a line of gravity that separates God from nature. So long as the seeker is within the boundaries of nature,
of the three properties,
God does not act.

While abiding close by the worshipper, he is yet only an onlooker. But when the seeker gets hold of the cherished goal with firm intentness, God begins to regulate his inner life.

The seeker then breaks free from the gravity of nature
and enters the realm of God.
God ever stands by such a seeker.
But he acts only for a worshipper such as this.
So let us always meditate on him.

I very sincerely bow down in lotus feet of revered Gurudev for all these learnings by HIS grace.

Humble Wishes!!!