Clio Expression 16v 2002 Immobilizer light always off?

The immobilizer light on my Clio is always off because of this it's very intermittent with when it starts up. Usually after leaving the car for a few hours it starts fine but if i turn the engine off and try it again after a few minutes it refuses to start. It will eventually start after several tries but it's extremely annoying. I only have the 1 key for the car and I have replaced the battery. Any ideas with whats might be going on and are there any solutions for this?

Thanks