I missed that you saw my point but for the sake of explanation I'll expound a bit.please
First, restraint does not only act on bad behavior. It merely limits possible behaviors. God the Father is restrained by love. "God is love". It's His nature. So what He does will always be consistent with love. The challenge for people may be to understand His love, but He will never act outside of love. By this principle He is restrained. Since He is all-powerful, this is a limit only He can impose upon Himself. No person or thing can restrain God since He is Lord of all. But He may willingly put limits upon Himself. And, because He cannot lie or deceive, He abides within His own limits.
Then Jesus before his death and resurrection was restrained by the flesh. He had to eat, sleep, and do all the menial things a man needed. He had to grow up from a baby to an adult, await adulthood to have any measure of authority within society, etc. By His example He limited Himself to do "only what He saw the Father doing". Again, this was self-imposed restraint. His flesh made Him vulnerable to temptation yet He never gave in to the desires of the flesh and remained perfect ("tempted in every way, just as we are—yet he did not sin").
Lastly, the Holy Spirit, sent by Christ after His resurrection, was restrained to only deliver what He was given by the Lord. "He will not speak on His own authority" ("..for He will not speak on His own authority, but whatever He hears He will speak"). So, He has an authority of His own, but He is willfully restrained to only speak what He hears from the Lord.
In all of this is the humility of God: how He humbles Himself to Himself, if you will. This should not be strange. He seals promises to Himself, too. And all of this is for our benefit. It's an anchor for our souls that He has chosen His Son (and all who are in Him) as the object of His love.