ok that is generally called bootlooping
in my list find android recovery
pull battery, hold home, replace battery , press power, release home and power when you see, triangle, !, and android andy
then press both volume buttons
select wipe cache, then select reboot
if still bootlooping, pull battery, wait 5-10 secs, replace, connect to wall charger, does it go into charging screen?
if it just bootloops may need to flash sbf
links to sbfs in my list, can try 604, if 621 is on phone, you will get a mem blank error and need to flash 621 sbf
but first you still can try safe mode, see my list
or wiping data in android recovery