1999 Jeep Cherokee car stalls

Hello, my first thought was, you may be losing the rpm signal intermittently? When the vehicle refuses to restart, have a helper crank it, while you check for spark at the plugs. You can also check for primary voltage at the coil and injectors, dark green wire with orange tracer, engine cranking.

Can you check for trouble codes? Some of the national brand autostores will check codes for free. The codes won't tell you what to replace, just that there might be a problem on that circuit/system.