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Sorry for the delay and thank you for your patience. My name is Michael. I will be helping you with your question today. I am an Expert in the Android Devices category. If you feel this is not the best category for your question, let me know and I will forward it to the appropriate group of Experts.
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This could of course, be a hardware failure, but let's put that aside - because if it is, then unless you really love the S3 too much to part with it, replacement might be the best option. But there are plenty of software issues that can cause this. The first thing I would do is make sure you do a complete restart of the phone. Power it down with the power button, or remove and replace the battery.
If that doesn't help at all, then I would do a wipe/reset - Tue reason is that this problem and similar problems are often caused by a corrupt system file, and a reset is the most foolproof way to correct them. You can do that under settings and then backup and reset.if you have any questions about that or about what you need, please.let me know. I will continue to help.