I changed the CVT fluid about 5K miles ago. I verified the level when I changed it just to make sure it was right. Definitely not a flat spot on the tires and just had them rotated and balanced with no change. The car only sits on weekends and I use it all week for work. It sounds like my car does exactly like yours. It will vibrate for a few miles first thing in the morning and then a few miles down the road on the hwy it completely smooths out. Doesn't do it to me after work though, just first thing in the morning after sitting for 12 hours. So I'm guessing since mine does the same thing as yours I should be alright....I hope.you may have said this earlier...but, when was the fluid changed last? have you checked the fluid level? might be worth the $30-40 to change it again. cheaper than the $120 to have a possible nothing is wrong charge.
i was going to say maybe the tires get flat spotted after sitting...but, you're in south texas and i don't think that happens often there, as much as it does here. my civic will vibrate for a few miles when leaving work when it's cooler outside. once on the highway, less than a mile from work...and up to speed...within another mile or two, everything smooths out. i should mention that happens to a much lesser degree since i put the Pirelli's on. the factory ones were the ones i was referencing too - continentals.