PG 33 of the manual tells how to manually disarm the system.
you need to follow the instructions that are on the little alarm sheet that has your alarm pin number code on it. it is done by turning the ignition kety off and on after a certain number of blinks appear that correspond with your alarm PIN code
Is the alarm going off or is it a buzzing noise? If you set the alarm and the interior light is set to the off position, then the alarm will buzz for about 45 seconds to let you know that it is not fully armed. Also if you attempt to arm it with something open like a door, it will buzz and that sensor will be disabled.
You can try to resych your transmitter (see pg 35 of the manual)
Make sure that the trunk is closed, and that nothing metal is in the cargo net that could interfer with the motion sensor. There are also sensors on the front cover panels, so make sure that they are not loose. I think if you put the key in the igintion, turn it to on, and then hit the little button it will go to valet mode and the alarm and immobiliser wont work.
Dumb question, do you have anything like fuzzy dice hanging, from your rear view mirror that might sent off the motion alarm?
OFL had a mouse in her car, maybe a stray animal may be lurking in yours.
It says the motion sensor is some sort of microwave based thing. I have no idea of how they work. Do you have a pacemaker that could be setting it off, or if your are using a microwave in your house maybe it is setting it off? Dont know if this is posible or not but who knows