gearbox fault 1999 range rover

Driving at 70 mph, fault code gearbox fault lights, engine stops. Cannot start. Wait 30 minutes, engine starts, gearbox fault code not on, says service engine soon-drive another 30 minutes, same thing occurs, wait 30 minutes, then restarts. What is wrong

i am no expert but this has happened to me on a 97 range and it was a quick fix all i did was replace the fuse on slot F17 and that worked. On a 98 range this happened to me when starting the range the gearbox fault would come on and the car would not start replaced the battrey and that resoved that problem..... Good Luck