HELP! Vortex shut off, won't turn on

[pmgmsd]

I have an LG Vortex. I've had it for 6 months. Phone has been awesome, except within the last month it has been shutting off randomly and isn't holding much of a charge. Every time it's shut off I've been able to get it back on, but today it died on me. I used FB app and made a phone call today. Nothing unusal. I left my phone inside while I did yard work for about 3 hours. I pick up my phone, it's dead, had at least a 75% charge when I went outside. I can't get the phone to turn on. I took the battery out. I plugged it in, left it alone for about an hour, still won't turn on. I've used both of my chargers. One came with my phone and the other is a car charger. I am at a loss. Any ideas? I haven't dropped my phone or gotten it wet.