Suspension Noise problems of the 2004 Toyota Avalon

I've noticed that sometimes I smell something burning, electrical, coolant or something. My mechanics finds no leaks, but I checked once and the coolant reservoir was empty, find no leaks. Somehow, the passenger side rear mud flap came off and the trunk lid doesn't line up. It always looks like it's partially opened. When driving I hear and feel rattling sounds that sounds and feels like the front passenger side suspension or body panels. More like the suspension. The person I bought it from had it serviced regularly and had timing chain, O2 sensor, anti-lock brakes checked and fixed or replaced. They also had it completely checked out and anything wrong was fixed. It also gets very poor gas mileage. The steering also doesn't feel quite right, can't really explain that very well, other than it's no quite right. Also, for some reason the battery wouldn't start the car one day and we checked the battery and the cells were dry.