Car randomly needs to be jumped

My husband's 2002 cadillac sts randomly won't
start, usually it happens when he's at work. He will
start it at home just fine, drive to work, sit in his car
during his breaks and have the radio on, but when
he goes for his last break or to leave for the day it
will be dead. It will start up easily with a jump and
not have issues for a couple more weeks and then
happen all over again. The battery is only 2-3 years
old. Also, and I don't know if it's related, it's saying
to service the security system.