I just bought a used iPhone 4 32 GB and I've noticed the screen flickers. It flickers almost barely most of the time and you have to be in a super dark room to notice (this doesn't bug me) but sometimes I've caught it flickering intensely for a small period. This has happened only twice, and I know it happened once when I was in a phone call (this may have been a software bug, as I've read if you initiate a data transfer the screen flickers) but at other times the screen will be totally black after unlocking the device, or just randomly turn black. I don't mean dim--I mean the device has a black screen with the image visible only in direct sunlight. This seems to happen ONLY when the auto brightness is on. I even have the brightness on the highest setting and check auto brightness and it will still do this. The home button and the lock button won't fix it. After about the third lock of the phone it will brighten back up. I'm wondering if anyone else is having this problem. My firmware is 4.3.1. I think the sensor may be bad. It doesn't have water damage (the headphone jack on the inside isn't white).
Does this sound like a hardware issue? The warranty on my phone is good until January but I'm still waiting on the confirmation email (after 24 hours) for it to be transferred into my name. How long does this usually take?