Nothing wrong with your head shape. And head shape is the number one question we get from guys considering a head shave. It is almost never an issue.
I made the decision at an early age that I would shave before MPB became noticeable on my head. But for me, that did not occur until my late 40's. You appear to still have plenty of hair and you are likely the only one that knows yet. I notice my thinning probably 3 years before anyone could tell.
If you want to shave, do so. It will look fine. But I suggest, while you still have hair, try every hairstyle you have ever though about trying. Enjoy your hair while you have it. Then shave when the thinning becomes more noticeable.
