1997 jetta "trek"

I have a 1997 jetta trek edition. Lately, the car alarm has been going off for no apparent reason. When I get in the car and shut the doors and then try to get out of the car, the alarm sounds. So, I have to turn the car off and disarm it outside using the key. Also, the alarm has engaged when I turn the key to start. When I start the car, the alarm goes off. I then have to disable it using the key outside. Thanks for the help.