Less than a month old MacBook Pro 2017 lags

So every now and then my MacbBook would lag (it lasts for about 20 seconds before it returns to normal.) It's about 3 weeks old, my desktop has no files displayed, I've got no files in downloads either, all unnecessary files in the trash are deleted, i barely have any documents, I've got 94.02 GB available out of 120.01 GB. I've got no other apps on it besides Skype, Spotify, and Telegram (I downloaded these from their official site), and I also installed Malwarebytes just in case. It started to lag when I was adjusting my brightness, it would adjust at least 1 level every 5 seconds (it took that long.) Earlier today, I had two windows (Safari) open. One window had two tabs open, while the other had 3. One of them being Google Docs. I figured the source of the lag was the doc but I didn't have any windows open when the first lag had occurred.

Is this normal? I was so excited to get a Mac but after experiencing this, maybe not so much

Specs (if needed):

processor 2.3 GHz Intel Core i5

Memory 8 GB 2133 MHz LPDDR3

Graphics Intel Iris Plus Graphics 640 1536 MB