my phone will not turn on all the way, shuts off and turns on repetitively
I hope you don't care about all your data because I don't think there is a way to retrieve it. Perhaps people with more knowledge than me know how (perhaps using ADB?). However, if you want to resurrect your phone, you need to follow this guide:

http://www.ibtimes.co.uk/update-galaxy-s3-i9300xxugnh4-android-4-3-stock-firmware-1468061

This guide below is a bit more old but you can look at it's images so it will help you:

http://forum.xda-developers.com/galaxy-s3/help/guide-odin-flash-guide-t1671969

The first guide will help you flash a 4.3 stock ROM to your S3 to revive it, but please make sure it's model is GT-I9300!!! If you have a Verizon or any other variant you may risk bricking your device.

Good luck.