iphone wont start

If you already tried (to no avail) ALL the steps provided in the support article that led you here, it might be a different hardware problem (battery? digitizer? other internal component?), but we, just users like you, cannot diagnose that kind of 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.

Did you follow the steps in the Related Article listed above? The final step is to use the link to contact Apple Support.