All Lexus models with auto-leveling HIDs go through that cycle you described. I can at least speak for the S2000 when I say that not all cars with HIDs do that. Then again, the HIDs on the S2000 are not auto-leveling.
My understanding of the "auto level" feature on the IS300 headlights is that the lights adjust themselves based upon the car's load.
So the lights don't adjust as you go up and down hills while driving, they adjust according to how your car's body is sitting in relation to its suspension. Two football players in the backseat (hope they're short!) would make the rear of the car lower, raising the front-end, which would cause the headlights to slightly lower their aim.
actually I think they do adjust if you are up or downhill, or over a bump. I have seen the beam from my headlight just jump up or down when I am on a bump or on a slope. I still like watching the headlight adjust itself, especially when you first start the car (the most obvious time), even after 3+ month of ownership.
BTW, after driving the IS at night and then drive my dad's 99 RX w/o HID, the headlight of RX just seem like it is turned off. Never realize how big of a difference HID makes compare to normal head lights.
Daniel - you're seeing things, buddy. Check out this from the IS300 FAQ:
How does Autolevelling HID work?
A computer instructs electric motors to vary the vertical aim of the headlights based on input from sensors in the front and rear (drivers side) control arms. The aiming seems to be done when the vehicle is first started, and does not respond quickly enough to compensate for body motion when the car bounces over bumps and potholes.
Sorry - I will revise the FAQ - now that I own and IS300 I can see that it DOES in fact vary the aim dynamically as the car moves. When I slam on the brakes they soon aim upright to compensate. When I accelerate they soon point down more to compensate...
Daniel - I apologize.
Apparently TEG, who knows a lot more about IS300s than I do, has seen the same headlight behavior you've seen.
So, you are right...and I'm going for a cruise tonight to check out my adjustable beams!
Actually, the best way I found out tonight is like what TEG was saying. You should find a place where you have a dark wall or large object at the end of the street, approach that object so that your headlight can shine on it. You will see that when you start braking kind of hard, the headlight will dip down first (normal reaction due to front end sag), and then all the sudden the light beam will jump up. Pretty cool to look at.