Try this first:
Hold down the power button and the home button together until you see the Apple logo.
Let it reboot and see if this helps.
The iPad iOS operating system is designed to shut down apps when system memory is running low or if an app is consuming too much memory (the top bar may turn red with a warning message).
You may simply just need to double-tap the home button to bring up the multitasking bar and teminate unused apps (hold the icon until it jiggles, then tap the cross) to free up memory. Alternatively, get the app XSysInfo, which will give you a detailed list of current processes running as well as two levels of memory cleaning to reclaim and optimize unused system memory. Doing a reset, as described above, is usually one of the last things I'd try.