How to fix a tablet when a white screen shows up really fast

Solution
With so little information from both of you, I can only sugggest that you power off the device then hold down the Volume Up button while pressing the Power button to turn it back on.

You should see a menu of options and I suggest Factory Reset. You navigate up and down the list by using the the volume buttons and select with the power button. If they aren't all backed up, the data will be wiped out but it should take the tablet back to a working state.

Before you do any of this, try connecting your tablet by USB cable to a PC or laptop. If it shows up on the computer, you might be able to remove personal files and photographs, etc.
With so little information from both of you, I can only sugggest that you power off the device then hold down the Volume Up button while pressing the Power button to turn it back on.

You should see a menu of options and I suggest Factory Reset. You navigate up and down the list by using the the volume buttons and select with the power button. If they aren't all backed up, the data will be wiped out but it should take the tablet back to a working state.

Before you do any of this, try connecting your tablet by USB cable to a PC or laptop. If it shows up on the computer, you might be able to remove personal files and photographs, etc.
 
Solution