Why does my car shake even when I hit small bumps in the road.?

I have a 2000 Lexus RX 300, and lately the car shakes very badly even going over small bumps. I am not sure if it has something to do with the shocks or what. The tires are less than 5 months old. It just seems as if my care does not absorb the impact of riding over imperfect areas on the road. Any mechanics or or auto savvy with advice. It sure would be appreciated. I just want to figure out what type of repair that is going to be needed. Thanks.....