my alarm is malfunctioning, often going off on its own- on 1999 Porsche 911

car has 145000 miles. recently alarm malfunctioning and emitting lite on dash not appearing at all.

Asked by for the 1999 Porsche 911
It could do this for many reason which requires an OE diagnostic computer, but I'd start by checking the battery with a good battery tester.
This would be the first and cheapest test.