Land Rover Repair: 1995 Land Rover Discovery, land rover discovery, factory workshop

Question
shuts off while driving & after sitting for awhile it starts back but at times after starting. it will not stay started when put in gear

Answer
There is no single cause for this problem in a 1995 truck, and it does not have the sophisticated self diagnostic system found on some newer vehicles.  You are going to have to test the basics, when it fails.  Has it lost spark, or fuel?   It's going to be one or the other.  The procedure for testing the ignition and fuel systems is fully detailed in the factory workshop manuals (available from many sources online) and requires only hand tools and a good multimeter