Why my iPhone X keeps turning off by itself?

I bought it in July 2021. The battery capacity is at 88.

The iPhone X was discontinued by Apple in September 2018. So, you either bought a used iPhone X or if it really was new........the phone sat on a shelf in a warehouse for 3 years.......which would not have been good for the battery at all.

Although the Max Cap is still at 88%, your battery is probably at least 7-8 years old, so my recommendation would be to make an appointment at the Apple Store or take the phone to an authorized Apple service shop to have the battery checked and tested.

You can find a list of authorized shops in your area using this link: Find Locations

Good luck.

Hello~ Same question as * Bob Timmons * …what’s your battery health? Go to Settings  > Battery, then tap Battery Health & Charging. Post back. Likely you need your battery replaced if it’s at or below 80%…

Genius Bar Reservation and Apple Support Options - Apple

Find Locations

Also try a forced restart…

Force restart iPhone - Apple Support

~Katana-San~

When was the last time that you replaced the battery in the iPhone X?

What is the current Maximum Capacity of the battery? Settings > Battery > Battery Health & Charging

Vevette17 wrote:

why is my iPhone X keeps turning off by itself? I restart it, it’s fine for a while, then it keeps turning off.

There is too many variables involved.

What are you doing with your phone when it turns off.

You have also have an old iphone too.