does it happen after jumps, or just driving around??
does the steering cut out also?
is it overheating?
check
- wires for kinks/brakes
- loose solder joints
- bad solder jab on the posts/motor
- loose plugs on the RX/motor/batt
- make sure the switch is working properly and not flipping off when jarred
- cut wires(especially the RX plug, and switch)
- make sure the sensor plug is all the way in(if using a sensored motor)