Honda Hybrid vibration

My 2005 Honda Civic Hybrid has 70,000 miles. When accelerating from a stop there is a vibration almost like I’m in 2nd gear instead of 1st gear, but this is an automatic. I’ve had a mechanic look at it and they can’t find the problem without costly tests?? Should I be concerned?

If you have a power train warranty, go back to this dealer and make them fix the car. The tests are on them, whatever the tests might be.
If I was an honest mechanic looking at your car, I’d check for a bad u-joint first. In any car, this is the circuit breaker for the power-train, a part like a fuse that is designed to fail under the first sign of stress. It is a very easy and cheap part to repair. It is even easier to check.
If your mechanic or dealer is playing games with you, get someone else to look at the car. Get references online to local repair shops, ask friends, etc. I think you are being asked to spend a lot of money to do nothing, and that you will be sucked into an expensive repair after paying for expensive “tests”. Find someone else to fix the car.
The fact that there is a vibration accelerating in any gear is an issue. Is there ever a clunk noise (sounds just like that, “clunk”) when you shift from neutral into gear? If so, the problem is almost certainly a u-joint, which a crook would charge you as much as $100 to replace. A master criminal would try to turn it into a thousand dollar repair.
I tagged this in case you have an update and need more help. Please let let me know how it goes.