From your link I would hazard a guess that it has the cheap 3D printed spindle arrangement so take care as they are unreliable for any real machine work. DO NOT over tighten the spindle motor clamp bolts.
Also did you pre-fill the bearings with grease as the oil in there is only a very light shipping oil and no good for long use ?
Its easy enough to loosen the bearing rods and slide them out so you can grease them properly.
Best way is to pump some lithium grease in there or EP2 gp grease and then hold your finger over one end and push the rod slowy in and out to force the grease into the bearing runs.
There are a few simple mods to these machines that I highly recommend and the first would be the HOLD, RESUME and STOP buttons.
The GRBL programs also have these on screen options but the actual physical buttons are better than rapidly screaming a mouse around a screen.