1997 Toyota Camry Vibrations

I put new shocks, new brakes shoes and Drums
new rims and new tires but my car still vibrates in the seat. The vibration is inconsistent it starts from 40 Miles to 60 miles. Some time I do not get any vibration.
I had few mechanics look at my car and they all were guesing.
Some say the Drums are warbed and some say the tires are bad. I am suspecting the bearing or loose suspensions.
Please help.