Ford F150 factory installed alarm problem

My factory installed alarm in my Ford 1998 F150 keeps going off at all times of the day and night (lights and horn). It happens several times a day. There is no apparent reason. We have remote entry but it happens even when the remote is sitting on the shelf. When we hit the panic button the alarm stops. Anyone know what could be the cause and solution? It's driving us and our neighbors crazy. Help please......