I would be concerned too if my iPhone was acting this way. It sounds like it is overheating and not holding a charge. I recommend following the steps listed below when experiencing an issue like this:
Battery life seems short
- Click ( www.apple.com/batteries/iphone.html) for tips on how to prolong iPhone's battery life.
- Try turning iPhone off and then on again.
- Connect iPhone to iTunes and restore iPhone.
- If the screen shows a low-battery image, the battery is low on power and needs to charge for up to ten minutes before you can use it.
- When charging iPhone, make sure to leave it charging until it is fully charged. You'll know the battery is fully charged when the battery icon in the upper-right corner of the screen looks like this .
Note: When charging using a computer, don't connect iPhone to a keyboard. Also, the computer must be turned on and not in sleep or standby mode. If iPhone is connected to a computer that's not turned on or is in sleep or standby mode, the iPhone battery may drain.
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All the best,