Slight shudder when coming to a normal stop

About four days ago, while driving my car, all of a sudden the check engine light came on at the same time that the car started to shake. I could not accelerate it very well and pulled over and had it towed. The mechanic found a cracked hose and all the coolant had leaked out. They replaced the hose and the coolant, and made sure there was no further leaks or damage.

Since leaving, I noticed that there was a slight shudder when my car would come to a normal stop. I had not noticed that before. It also didn't seem to accelerate as easily. The mechanic told us to bring the car back and we did. They cleaned everything out and checked everything, including brakes, and drove it around and found nothing wrong. They said the car was fine. The problem hasn't gone away. I asked a couple of mechanic via phone and they didn't know what would cause that.

Any ideas, or am I just being paranoid?