you need new battery. OE batteries last about 4-10 years, as proven by members on this forum, non-OE batteries last 2-5 years, again, as indicated by the members on this forum...

in your case, it would be a good measure to replace the battery, as they usually go without warning (well, electrical gremlins are the warning - like the alarm that you are experiencing) and the car may leave you stranded - you go to a local gas station, pump gas, get back into the car and it is DEAD... happened to many of us... lol... myself including!!!