I totally get the stress with a new car, especially when something goes wrong right away, like your thermostat! At least the garage fixed it fast. You might still feel nervous until you take it on a long drive without any problems, so maybe try a weekend trip to chill out a bit.
Also, I found this cool article about how new cars get transported, and they really take good care of them. Same should go for used cars if you bought from a good place. It’s worth checking how your car was handled to avoid issues. Here's the link if you're curious: https://www.a1autotransport.com/how-are-brand-new-cars-transported/