my phone goes to the apple logo then it fades out and restarts like 10-15 times, then it turns on and when i try to unlock it it starts over again. PLEASE HELP!!

my phone started off going to the apple logo then to a blue screen then it would fade out and restart. it does it multiple times so i updated it. it was fixed for about an hour but its been going to the apple logo and restarting for about an hour now and it wont just turn on. its a brand new phone i just bought from the insurance company. (sprint)