Chosen Solution

My phone keeps turning off even when the charge hasn’t finished so I can’t use it and it won’t come on so my question is that why does it do that and what can I do to prevent it happening cause it only works every three days when I put it in charge

I agree with the first answer. If your battery is older than 2 years it might be time for a change.

Try a hard reset. Press and hold the power and home button until the apple logo appears. If that doesn’t work, replace the battery.