Hi, my Blackberry Q5 suddenly turned off in the middle of a text yesterday, and since then has been stuck in a turn-off/turn-on cycle. It had over 50% battery when this happened. I've let the battery run out since I couldn't turn on or off my phone and have plugged it in again. It started that same cycle again but is now stuck with no screen activity and a slowly flashing yellow LED. What could be the problem and how do I fix it? Thanks.