Hey lujainsj,
It sounds like you have a concern with the iPhone powering off, and you're unable to access it before it powers off again.
Here's a resource to follow for the exact issue that you're experiencing. Follow through these steps:Â If your iPhone won't turn on or is frozen - Apple Support. If you're still unable to turn on the device after going through the resource, you may want to look into service options.
Take a look here to find some nearby service locations:Â Apple - Find Locations
Here's some information about seeking service:Â iPhone Repair - Official Apple Support
You can also start a repair request here:Â Get Support.
Cheers!