Car doesnt start immeditately. security light comes on. once security light goes out car starts. Why?

It is detecting a problem....could be a dirty key or bad chip in the key....try this.....set the alarm by locking the door using the power lock switch and then close the door...the security light should come on steady for about 2 minutes and then go out.....the alarm is armed at this point.....you can unlock the drivers door using the key to reset the alarm.....if you do this with the windows down you can open the door from the inside to set the alarm off and see if it works properly by flashing lights and horn....after you trigger the alarm you will have to reset it by using the key on the drivers door....