The first culprit to check for is an old or failing battery, these cars are very sensitive to battery condition and do all sorts of weird and wonderful things when the battery is dodgy.
If you still have the original battery in an 09 then it's well overdue for replacement.
The second thing to check for is a stray critter crawling around inside, do you get big spiders in your neck of the woods?

 

Can you pull the codes from the system? It will tell you the last (10?) triggers for the alarm. Typically your symptom is a failing sensor for one of the doors. The bonnet/hood is often the culprit. If you can work out which one it is, it's pretty cheap to replace