I have a 1999 Camry LE. I bought it used at 95,000 miles. I recently got the timing belt replaced, transmission fluid flushed, and an oil and filter change.

All of a sudden, the car has been vibrating at really high and low rpms (vibrating more than it was before and more than I think is usual). This never happened before, and what is stranger, is that in the morning when I drive to work in 20 degree weather, there is no vibration!
The car only vibrates on the drive back home when I go beyond 2,700 rpms and lower than 1,200 rpms (I drive 60 miles one way to work and I don't drive over 80 mph). When I am in between those two marks, the car is as smooth as butter.

Could this be caused by any of the changes I mentioned above, like the timing belt replacement or the oil change and the transmission fluid flush? Also, my drive consists of 15 miles of traffic driving, 30 miles of 55-60 mph driving, and 15 miles of highway.

I really need some help, because I am worried about my car!!!

I am no expert on the subject but I think you should double check
the trans fulid level.

Also check your tires. My mom's toyo van vibrated at low and high speeds (but not in between) and it was because of uneven wear on the tires.