I double tap my iPhone 4S for multitasking the screen goes black it has the loading logo in the middle of the screen?

It sounds like your iphone 4S is experiencing a software issue, possibly related to multitasking. This black screen with the loading logo may indicate that the device is struggling to process tasks or is stuck in a loop. Try performing a hard reset by holding down the Home and Power buttons simultaneously until the Apple logo appears. If the problem persists, consider restoring the device using iTunes or checking for software updates.