Frequently frozen phone, software or hardware issue?

Hi all,

My Galaxy S5 has been a real bear lately. At least once every single day, the phone completely locks up. Usually it's with the screen on, but other times has been while the screen is off and I can't get it to turn on. The weird part is that if there's an animation on the screen (like the battery charging animation), the animation still plays but everything else is just stuck. The only way to fix it is to battery pull or hold down the volume down + home + power buttons and force it to reboot.

This happening every day, at least once if not more. I've flashed different ROMs hoping that it was just a ROM that was the issue, but it doesn't fix it. When I flash the ROMs, I make sure to wipe everything except the SD card so it's a very clean install, but alas no bueno.

I'm about at my wits end and ready to go to the AT&T store today to turn in my phone and get a Nexus 6 or Galaxy S6, but thought maybe someone here may have ran into the same issue and was able to resolve it.

any help appreciated - thanks!