Try to get a bike fit first. Ideally after some basic stretchwork / few classes of mobility training just to get the feel of what Your body is capable of in the short term.

It sounds like waste of money for something people feel like they should be able to judge themselves, but bikes aren't shoes. The issues often develop only after some hours of effort. If You're a beginner, chances are the flexibility of Your back / hips / joints will be the most limiting factor.