The apple logo on my iphone is frozen, what should i do?

i have an 16G iphone and my iphone doesn’t start up past the apple logo…it just stays on the logo ITS SO FRUSTRATING!! and i don’t have a warranty on my iphone because i got it from the internet and i tried calling the apple company and they say they can’t fix it because i don’t have a warranty…is there any way i can BUY a warranty or DO SOMETHING????? ive tried rebooting AND IT DOESN’T WORK!!!!!!! PLEASE SOMEONE HELP ME!!!!!!!!!!!!