Is a Roman Catholic obligated to believe in the Trinity? There are many people who are technicially born into Christian homes, yet they don't fully agree with the doctrine of Trinity etc.

According to the creed of Roman Catholic Christianity, if someone is not 100% comfortable with the concept of Trinity (that is, believing it without a doubt in their mind), does that automatically make them 1) a Non-Christian and consequently 2) go to Hell
Trinity is a Dogma of the Catholic Church. Hence as with all dogmas a Catholic is bound to believe it in order to maintain the bond of faith.

You have asked: if someone is not 100% comfortable..... Who is this someone? If they are non-baptised person, Catholic church has no official stand regarding them, only God will know.

If they are baptized Catholic then:


Once a Catholic always a Catholic. Even a excommunicated person is a Christian who is not in union with the body of Christ. Baptism leaves a indelible mark on your soul.CCC 1272
No-one can be sure about any specific individual will or will not go to hell. That is, only God can tell whether they will be saved or not. But if they are willfully refusing to believe a dogma, a divinely revealed truth, proclaimed as such by the infallible teaching authority of the Church, then it can be implied that they are refusing to remain in the church. And those who refuse to remain in the Church will not be saved.CCC 846


One being not comfortable is different from one says he believes Jesus is not God. Your question title and its content differ in its meaning.

If one is not comfortable:

Please remember you don't have to understand a dogma to believe it. So, you can believe in a dogma even if you have doubt. All that is required is your full will, For as long as one remains willing to submit to the Church's decision he remains a Catholic Christian at heart and his wrong beliefs are only transient errors and fleeting opinionsCE : Heresy.

If one says he does not believe in a dogma, and they fully understand the way they are in disagreement with the Catholic Church:

This will make him a Heretic. A person who obstinately persists in heresy will not be in union with the church and hence cannot be saved.