Bluetooth turns phone off?

I just bought a new vehicle with bluetooth installed and I've noticed that if I drive somewhere, when I get out my phone has mysteriously turned itself off. I can turn it back on with the power buttion, but this is annoying. Does anyone know a solution to this problem. The phone is an 8330 with Verizon service, 4.5.0.77 software. Thanks!

Does anyone else even have this problem? Is there a sleep mode the phone goes into with bluetooth that I don't know about? I know it will go into sleep mode, but usually when I push a button it comes right back. With this bluetooth thing, I push buttons and nothing happens. It's a pretty annoying issue to have....