There’s a simple guiding rule: if your happiness is mainly affected by difficulties within the relationship, it’s best to come together. Working as a couple is often the fastest and most powerful way to improve your situation.
If your partner is hesitant, try to encourage them to join for at least one session. If they still refuse, come on your own — we can explore ways to involve your partner later, or we may find that starting individually is actually more helpful.
There are also situations where it makes more sense to come alone from the beginning. For example, if you want to work on personal topics your partner is tired of discussing, or in cases of violence, abuse, or (co-)addiction. In these circumstances, individual consultation is the safer and more constructive choice.
Whenever a change of setting could benefit you, I will suggest it. But ultimately, you remain in control — you decide what the next step will be and how you want to continue.