Mine (rx350 07) does both of those things too!
literally i have been to lexus 5 times for the tire pressure thing. they adjust it every time i take it in for an oil change. it seems like the light is always on even if the tire pressure is fine. it is just really, really annoying. they "fix" it every time i am in there and it always comes back on. it came on 3 days ago, went off and was back on today when i was driving home from work!
the shaking thing it more of a concern for me. one of my friends drove it and he said it feels like the brakes/roters. i am not looking forward to that service bill!
i love my rx but with as much as i have spent on maintnence i am for sure going with bmw next time i buy.