Jaguar S-Type starting problem

Everything seems to work fine such as battery, starter. When I try to crank the car the dash board meters lights go dim as the battery would respond as it were low in power but rest of the lights work fine. It has happend few times before but on playing with key and gear stick it eventually cranked. Seems like on turning the ignition key, signal does not go to starter so it does not crank. It behave like if there was a sercurity switch. Previously with few tries I had been able to start my car but now it becoming more difficult to make it work. Please suggest.