Robot Reboot?

[Team 4457]

Hello, We have been having a major problem with our robot's performance in competition. In last year (2013)'s competition as well as a local competition, we had the problem of our robot losing power on the field. When i go into the driver station log, it appears as if the voltage going to the cRIO is spiking and causing it to crash. But we have been told that the cRIO and/or the power going to it is probably not the main issue. In last year's competition it would mainly happen when we were driving our robot, then activated our shooting mechanism. But at the local competition, it would happen even though we were just driving (albeit with four motors). Does anyone know what is happening/ why its happening/ how to fix it? Thank you all!