Why is my iPhone 15's battery health at 97% with only 35 cycles?

No, it’s not normal, it should be 99% with 35 cycles, but that is greater precision than accuracy because the battery gauge isn’t linear, so see what it does going forward.

Are you following best practices for battery management?

• Turn on Optimized Battery Charging (not Charge Limit)
• Charge overnight, every night (Added benefit - you can enable automatic overnight backup)
• Charge if it goes below 20% during the day (it generally won’t)
• NEVER, EVER, let it go to zero and shut down - that is about the only thing you can do that will shorten battery longevity.

That’s the short answer; here is the long→When to charge your iPhone or iPad | Communities

Lawrence Finch wrote:

If it’s only got 35 cycles it was almost certainly new.

There's "new" and there there is "new"...

It could have been sitting on a shelf somewhere since September of 2023... or it could be gray market, or it could just plain be used... Based on the user name, my money is on some combination of those. I'm also going to guess it originated from a country other that the one where the OP acquired it.

mredul_hasan wrote:

please help me what should i do right now?

As I said, don’t do anything right now. Just monitor it.

mredul_hasan wrote:

please help me what should i do right now?

Exactly when and where did you purchase it?

Did you buy it directly from Apple? From a cellular carrier? From a retail store? If a store, what store?

If it’s only got 35 cycles it was almost certainly new.