How do i reset my phone to default settings on my samsung sch r451c straight talk phone threw usb and my pc?

Without actually pressing any of the phones keys becasue every key i touch restarts the phone i was in the hidden menus of the phone and all the sudden it restarted and now its on roaming and displays phone off and any key i touch turns the phone off then rite back on so i cant get into the menu settings to restart the phone because the first on i prees turns off the phone so i need to restart it threw my pc but im not able to pull up any of the info of the phone when i plug it into my pc and im so mad can someone please help?