I am no structural engineer, but I think that a few narrow (narrow meaning you cannot stick a pencil in) cracks are common with new and fairly new slab foundations. Problems arise when the cracks show differential settling (I think that is the term), meaning one side of the crack is higher than the other.
A good indicator of problems would be cracks in the drywall above the top corners of doors and windows.
Yeah, look above the doors in each room - if the cracks go straight up, no a big deal. If they are diagonal to the sealing that is usually a bigger problem.
My career for the last 10 years has been centered around foundation failure. The direction of cracks is irrelevant. What type of foundation, where are the cracks, where is the home, terrain, how old is the home, describe the cracks, etc.
I'm having PTSD as we speak. Foundation redo on my old house, tunnels dug under the house, piers put everywhere (slab foundation), lawsuit against insurance company. Ugh, I'm getting the shakes.
I used to do foundation analysis and inspections as well. You can hire an engineer to analyze it and give you a report. The engineer should take elevation measurements as part of his/her evaluation.