Need your help at the earliest friends.....
More details about your situation please?
Users often forget to give specifics such as;
Firmware version (Developer preview, Cyan from your carrier, No update etc:...)
Carrier
SD card installed\not installed
Recent app downloads including "betas" or any known problem applications.
What you have done to alleviate your issues...
It is difficult to guess what is happening when we have no details about your problem.