Phone freezes ?

[j77drummer]

So my friend bought a 6700 on ebay and i am trying to help him out with it. The phone keeps freezeing after being left alone for about 15 min or so. its is running the original verizon rom and I have done a hard rest and it still does it. any suggestions i dont want to flash if i am gonig to have to tell him to send it back. thanks in advance