For those who don't believe baptism is required for salvation, when, scripturally, does someone die with Christ? Paul recites as part of an early creed.

2 Timothy 2:11 ...If we have died with him, we will also live with him;...

Here it seems that our living with Christ is conditioned on us having died with Christ. The only place in the scriptures where we are described as uniting ourselves with Christ's death, I am aware of, is through baptism:

Romans 6:3-5 3 Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? 4 We were buried therefore with him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life.
5 For if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his.

(*See also Colossians 2:12 and surrounding verses)
(I've significantly edited my question for greater clarity based on responses below)
For those who do not believe in baptism for salvation please answer specifically the following questions:

Do you believe it is necessary to have died and been buried with Christ in order to be saved? If not please provide a biblical basis for why not.
Do you believe that we are not buried with Christ at baptism?
If not, what is the biblical basis for believing that we are not united with Christ's death at baptism?
If you believe that we died with Christ at belief (or at some other time), what is the biblical basis for claiming that our moment of death with Christ is the moment we first believed in Jesus Christ specifically or some other specific moment?
Anyone who says that baptism is required for salvation must therefore be saying that baptism in some way has an essential effect for the person's salvation.
Those who say baptism isn't required for salvation generally say that it is symbolic of the real salvation effects of the death and resurrection of Christ. (Though many churches teach a Sacramental view, in which God does truly act through the sacraments, even though those acts are distinct from Christ's once-for-all mediatorial work accomplished by his death and resurrection.)
There are multiple views of what it means for us to be United to Christ, but the doctrine is most prominent in Reformed Theology, and in Reformed Theology it is the Holy Spirit who unites us to Christ, in faith. So the Westminster Confession says

WCF 11.4: God did, from all eternity, decree to justify the elect; and Christ did, in the fullness of time, die for their sins and rise again for their justification; nevertheless they are not justified until the Holy Spirit doth, in due time, actually apply Christ unto them.


WCF 11.1: Those whom God effectually calleth, he also freely justifieth: not by infusing righteousness into them, but by pardoning their sins, and by accounting and accepting their persons as righteous; not for any thing wrought in them, or done by them, but for Christ's sake alone; not by imputing faith itself, the act of believing, or any other evangelical obedience to them, as their righteousness; but by imputing the obedience and satisfaction of Christ unto them, they receiving and resting on him and his righteousness by faith; which faith they have not of themselves, it is the gift of God.