If you're not sure what rooting is, and if you bought your phone brand new, you're not rooted. But here's something to try:
Turn the phone off. Either by holding Vol up + vol down + power until the phone shuts off (or pull the battery out, count to 5, put it back in).
Then push Vol down + power. The bootloader will load. If your USB is connected, unplug it. Then go down to Recovery using the volume buttons and push power.
This will take you to a screen that has an Android character with a triangle with a exclamation mark in it. It's been a while since I used the standard Android recovery, but I believe if you push power, text will appear. You then can scroll with the volume keys again. Select "Factory Reset" and push power. If the only thing that happens is that the text blanks out, push power again to get the text to reappear and push the camera button. This does a complete wipe on your phone and, hopefully, clears out what ever is making your phone boot loop.
If that doesn't fix it, take the phone back to Sprint. Your device has a 1 year warranty on it, so they're still obliged to fix it.
