Heater intermediately blows cold air and temperature gauge fluctuates up and down while driving

I got a new car about 2 weeks ago, a 2025 Chevy trailblazer. Didn’t expect anything to go wrong but a couple of days ago I noticed the heater wasn’t as strong as it should be, and sometimes it’ll blow cold air for about a minute then go back to normal.

Also today I noticed that I’ll be driving for about half an hour and I’ll see the temperature gauge go down about a third of a bar then go back up and it’ll fluctuate a lot.