My phone just started locking up. When I turn it on the initial screen comes on looks like it is ready to swipe to get going. But, nothing happens. The screen is locked up and nothing works. Using the on/off button I can cycle it on and off but it takes removing the battery to get it working again. It just started doing this the last couple of days and has done it now about 7 times. Is this a bug? How do I fix it?