Those spiritually dead live "according to the course of this world, according to the prince of the power of the air, the spirit who now works in the sons of disobedience" (Ephesians 2:2). We were spiritually dead not believing the gospel of Christ. We were spiritually dead living by the spirit of disobedience. Our lifestyle was according to this present evil world. That's when we had no relationship with God.
Those spiritually dead come to new life through faith in our Lord Jesus Christ. "But God, who is rich in mercy, because of His great love with which He loved us, even when we were dead in trespasses, made us alive together with Christ" (Ephesians 2:4-5). Our new life comes by God's love and mercy in Christ. Because he lives, we are spiritually alive to God. Christ is our new life.
What did we do to deserve new life with God? The answer is nothing. It's because God was rich in mercy toward us. It was God's mercy and grace in Christ alone. You were spiritually dead, but now "by grace you have been saved" (Ephesians 2:5). By grace through faith in Christ, believers are spiritually alive to God with new life.