WHAT DOES IT MEAN FOR GOD TO BE SELF-EXISTENT AND SELF-SUFFICIENT?

“Now to the King eternal, immortal, invisible, to God who alone is wise, be honor and glory forever and ever. Amen.” (I Timothy‬ ‭1:17‬ ‭NKJV‬‬)

It means God is INFINITE “the King eternal”  Literally, He is King of the ages (so rendered by the ESV)—that is, God stands above all the ages—He was before all time, He transcends all time, and will rule over the eternal ages when time is no more—at least, not as we measure time.
 
It means God is INCORRUPTIBLE “immortal”  The word means incorruptible—a word Paul only uses to describe God—for it could not describe anyone or anything else, except that which pertains to God.  God cannot age, decline, or be defiled.  He is immune to the corruption we face.

It means God is INVISIBLE “invisible.”  Ref. 1 Tim.6:16.  God is a Spirit—and has no body—therefore He cannot be confined to a locality.  His presence fills the universe and transcends it.  The invisible God has only become visible in the person of Jesus Christ.  The glory of God is such our eyes could not behold His fullness.

It means God is INCOMPARABLE “God…alone”  The word “wise” found in some manuscripts isn’t found in the oldest and best—though it is certainly true that God has incomparable wisdom and other texts substantiate that.  He has incomparable wisdom, power, holiness, love, and all His attributes, because He is an incomparable Being—and that is the thought here.

He is God and God alone!