iPhone 5S won't boot, blank screen, chimes every 5 seconds.

After cleaning out lightning port with tooth pick and opening case to clean out lint and gunk around that end, the 5s would not start. When connected to iTunes via USB, it chimes (charging chime?) every 5 seconds. This was an extremely well taken care of phone, not dropped, no water damage, always in case with screen protector. It worked flawlessly prior to opening case (except lightning connection challenges well documented on web).

After chiming for a while, it gets warm to the touch behind the battery.

Any suggestions other than screen replacement. Please reply if you are familiar with the problem and successful resolutions.

FYI - iPhone 5s, updated to IOS 9.01

Thank you