iPad keeps going into recovery mode

I have a user with an iPad1 which keeps going into recovery mode and is becoming more frequent. The user will be switching between applications and will all of a suddent get a spinning circle. The only way to get out of that is to hold the Home and Power buttons to power it down. When it comes back up again, you get the USB cable / iTunes image on the screen. When the iPad is connected to my computer, iTunes displays the message "iTunes has detected an iPad in recovery mode. You must restore this iPad before it can be used with iTunes." I can get into the iPad using the iRecovery Tool and all apps and files are available.

The problem is, why does this happen and how do I prevent it? Is it a user error or hardware/software issue?