For more info go to the LG support site.
Basically, you will need to save all your personal data;
Try a soft reset, if that doesnt work: factory reset;
Also, ensure the latest software/firmware is installed.

LG 620 G turns off all the time have to remove and replace battery to turn on. I love this phone from strait talk it is simple usually gets good signals etc but it wont stay on and then I have to remove battery to allow to fully power down before I can turn back on dpont know if something is wrong with power save mode or what any help appreciated thanks