If you're in a commercial aircraft and the commercial aircraft starts to circle before it lands it doesn't mean anything is wrong.
The plane may need to be in a holding position to avoid collision with other planes at the airport and they may need to circle again before they can land.
If the runway is clear though when the plane reaches the airport then the airplane may just go for the landing and land without circling.
However sometimes the airplane needs to get closer to the runway before landing so they would need to circle again to get back around to getting in the correct position to land.
If it's a small airplane it could be that they need to increase their airspeed again before landing or it's a newer pilot that hasn't landed before and has to circle a few times before they are able to land.