From your description of the matter at hand it seems that you phone is stuck in a so called bootloop.
The first thing i would suggest is that you remove the SIM card in order to see if the bootloop persists without a SIM card mounted. If you have a SD card, try taking that out aswell. If the phone starts up as usual without SIM and SD card, the cards may be damaged and needs to be replaced.
If the boot loop persists without SIM and SD cards mounted I would suggest that you try to perform asoftware repair using a computer and Xperia Companion. Please note though that a software repair will erase all user data.
If none of these measures manages to get you past the boot screen i recommend that you get in contact with your local support team in order to have the phone sent to an authorized service center. If you have any questions regarding the service, such as routines, warranty and consumer laws, these type of questions are best answered by your Local support team as well, as they vary between markets.
Try these measures and and let me know how it goes!