I've had my phone for about 4 weeks, and for the last few days it just switches off randomly in. yesterday it would turn itself off and on again, literally every few minutes. Today I Can't get it past the blue screen, except for once, but then i touched it and it went off again. I've done the 'press volume down and power button till it buzzes' but it made no difference. Has anyone had this problem, how did you fix it?