Is it just throttle playing up? - most likely incorrect ESC setup, or maybe you've inadvertently adjusted the throttle trim tab/dial without realising whilst driving? (Easy done when you're being enthusiastic...)
OR is the steering twitchy too? (Or EVERYTHING suddenly goes unresponsive) - this will be interference (Caused by metal on metal rubbing of the metal parts, but mainly only affects 27MHzAM radio) or a dodgy power connection to the receiver, or even a dodgy receiver on/off switch (- has the problem only started since the car has been on wet grass or in a puddle?)
