I have a 2003 Toyota Camry LE V6 it has 247,000 plus . Change oil at 3000 to 5000miles with synthetic motor oil. Within the last year it's developed a intermittent shudder noticeable between 55 to 85 mph. The higher the speed the more noticeable the shudder at first I thought it was a brake, tire, or wheel bearing problem.replaced all with new except the bearings they seem OK.At 75mph the shudder occurs about every 3 seconds and last about 3 seconds. Im afraid the motor or tranny is going to sling apart and leave me stranded. Not good being I work 196 miles from my house.
Could be a misfire your feeling, check the coils and plugs. Is an automatic, maybe your feeling the torque convertor and the trans is starting to fail. If your afraid of the car failing, maybe it's time to look for something newer.
I vote for the torque converter clutch as Tom said. -Jim