how to fix boot loop on iphone7?

Logo Bootloop or Stuck on apple logo

see the process below

If your iPhone is stuck on the Apple logo - Apple Support

or watch this video 

https://youtu.be/2CRilTPouRU?t=97

There is no guarantee you can save any data since your last backup if you need to use the Restore option.

Try a "forced" restart of your iPhone, using these instructions:--> Force restart iPhone – Apple Support

If the issue persists, it might be a hardware (battery? digitizer? other internal component?) problem but we, just users like you, cannot diagnose that issue remotely, sorry.

I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector. After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.