Hi tainment, I too have a similar problem. I had the VSC/TRAC/Engine light problem others reference. Took it to a toy/lexus only shop today, they replaced the mass air element and now- no dash warning lights and it runs GREAT. It worked fine today (alarm did not go off) for the several times I set it, but tonight it started randomly flashing lights and beeping horns. Note that I do not even have to lock doors (arm the alarm) for it to go off. So what I did was to unplug the two horns (1 behind radiator, 1 in vent on drivers side of bumper) and an additional horn that seems to be only related to the alarm- on the passenger side of the firewall. So now it only flashes the lights every once in a while. Much less annoying for me and neighbors. That may be a short-term option for you.
Not sure if my problem is related to the service, not sure how it could be, but I don't know. It is raining (Hanna passes through NC) so maybe there is a vibration alarm set too sensitive? I've owned the car 2 weeks, 54K miles great shape otherwise.
