Motorola Atrix 4G :: Its Turning Off Spontaneously, Hot To The Touch

Periodically, the phone will apparently be off for no reason - and will not respond in any way, not even to turn on with the power button. I have to pull the battery and replace it in order to power it up again. Most of the time, when I discover the phone off, the phone itself is very hot. I've noticed when pulling the battery, that the battery itself feels fine - warmer than usual, but not as hot as the phone itself.Also, most of the time, after I get the phone up and running again, it shows a very low charge on the battery (like 20% or so), even though it may have shown 80% hours earlier. This part doesn't happen every time - sometimes it comes back up still showing a good charge. But most of the time, it shows a low figure.