2007 Nissan Altima steering wheel & front seat vibration

I bought my car in june-21-07, from the first day I bought there was body n steering wheel vibration, I went back to the company they told it's from the front tyres one of them is disbalance(Bridgestone), they replace all the four tyres for me(Maxxis) but the problem wasn't solve they told me it's a wheel balancing they made the wheel balancing at the same day it was solved but the next day there was the same steering wheel n front seat vibration, I went back to the company they change the four tyres with bridgestone again the problem was solved, but the next day again the same problem apeared coz when I was starting my car in the morning n wen I drive my car on the smooth surface road it comes on between 80-100 kmph, after all this situations one day I thought I should go my self n change the tyres from the bridgestone shop but I went to them n I had a talk they told me to have once more wheel balancing but when they made a wheel balancing after that there was nuthing the car was soo smooth just like brand new car, but after opening my tyres soo mamy time's there was a brake juder problem came, again I went back to the company they fix the brake juder problem but again there is steering wheel n front seat driver's vibration came back I dont know how to solve coz when ever I goes to company they says every thing is fine with your car, coz some times it comes n some times it does'nt, and the mechanic in nissan company says me when ever cars tyres will be open it needs wheel balancing and I dont believe this thing coz I have driven lots of car in my life but this is first experience in my life, plz if u can reply me wid good solution I will be very thank full to 2carpros team n management. Iwill be waiting for your good answer.