S3 turns itself off and partially on then off

[FilthyHands43]

My s3 sph-L710 turned itself off today while I was at work. It turns itself on to the Samsung Galaxy SIII logo then shuts off again. Pressing the on button seems to initiate it to turn on if I am pressing on the back near the battery about 50% of the time. Since this happened I have gotten to the home screen one time on my s3 and almost immediately after it shut off again. I got home and tried another battery and that did nothing. I plugged it into my computer and it will not show up on the computer. If I have it plugged in and try to turn it on the charging symbol when you charge it when it is off comes up for a second or two. I have had this phone since roughly Feb. when I had to have my old one replaced. I have read similar stories to this and saying it is the motherbord but it would not turn on at all if it was that if I am not mistaken. Anyway thank you!!!!