1997 Jaguar Xj6 Running Fine While Driving Shuts Off Start Let Sit Weeks Car

My jaguar was running fine. Then while driving it shuts off and then i start it up its fine. I let it sit for a few weeks.go look at the car. The dashboard lights come on. But it wont start. It cranks though. I got the battery charged. It ran and shut off. But the gas is near e. im confused about the problem. And when i turn the heat on the car shuts down. Whats the problem. Thanks