When I lock the vehicle to go off to the shops or the gym for example , everything seems fine at first but when I return the hazard warning lights are flashing quickly but there is no alarm sound. As soon as I unlock the vehicle the lights stop flashing. I am now unwilling to lock the vehicle as it seems to happen every time. I have only noticed this in the warmer sunny weather so could it be triggered by heat/direct sunlight?. It is a 2004 vehicle and I bought it in Nov of last year

Anyone had a similar experience?