If you are in a relationship, the decision about who should go to sex therapy can seem confusing. It might be that you are identifying a problem, but you feel that the problem is mainly related to your partner. Or maybe your partner feels that the problems are related to you.
In any relationship partners have to try and share responsibility for what is happening. It might be true that one person's behavior is, on the surface, creating a "problem" but our behaviors don't happen in a vacuum. For example if one person has lost all interest in having sex, it is likely not only the result of some internal change, but rather may be related to changes (or lack of changes) in the relationship.
Ultimately if a couple is interested in sex therapy they will probably have to go to therapy together. But if you are the one interested in therapy, and you would prefer to have an initial session on your own, there is nothing wrong with starting the process this way. Depending on where the therapy goes, you may or may not bring in your partner at a later time.