Original post by: PCHookups ,
Something similar happened to me but I later found out that the phone was exposed to liquid (albeit briefly). Another instance was I somehow broke off a microscopic piece on the logic board. Get a really strong magnifier and look at the logic board to make sure no jumpers,etc.have broken off. If you see something missing/damaged, it'll need to be microsoldered back on. Also look at the digitizer connection on the logic board to make sure any of the pins haven't been bent or broken. Age of the phone doesn't necessarily doom the phone, just the condition of it. Good luck and I hope I helped.