First, Adam and Eve do not believe that God intends to be good to them, and therefore they suspect that his commands are actually restrictive rather than liberating. The result of this first stage of unbelief is disobedience, and it is inexcusable. They should have known from the fact of their creation that God is good, always good.
Second, Adam and Eve do not believe that God will sustain them and all his creation in the face of their sin, and therefore they doubt whether he will show them mercy. The result of this second stage of unbelief is hiding from God, and this too is inexcusable. They should have known from the fact of their creation that God is committed to upholding his creatures in the face of the chaos and darkness that threatens them.
I sometimes wonder whether we could truly talk of fallen human beings if there were not this second stage; might they not have been just stumbling human beings, recovered by grace?
Corresponding to this, 1 John 2 counters both stages of unbelief in the Christian:
My little children, I am writing these things to you so that you may not sin. But if anyone does sin, we have an advocate with the Father, Jesus Christ the righteous.Believe that God is good and don't sin; if you sin, believe that God is good and don't hide!