intermittent starting issue

[mikeouk]

my 99 2.5 has an intermittent issue. It sometimes starts fine, i turn the engine off and go to start again and theres nothing, its not like a flat battery ,the engine doesn't even try to turn, also ive noticed some other strange things, on one occasion i tried to open the doors and the central locking didn't work, i opened the car with the key, the engine started fine, then as i was driving along i could hear the central locking trying to lock and the interior light came on, then when i turned the engine off and tried to lock the car the central locking wouldnt work, left the car for an hour or so and it was fine. Anyone got any ideas? its making me nervous of taking the car anywhere because im not sure if it will start when i come back to it.