One of the most common reasons why a sewing machine jams are because of the insufficient tension at the upper thread. It happens because the machine does not get sufficient tension to pull the thread, solution for this is to lift the presser foot and rethread the needle.
Another reason for sewing machines being jammed is dust or debris, they are stuck inside the machine and cause it to stop. The only solution to that is to properly clean your sewing machine.
The sewing machines often stop working because of bent or broken needles. If you face this situation, make sure you properly check the needle and replace it if necessary.
One of the common problems due to which a sewing machine stops working is because the feed dogs, do not work properly. It mostly happens because of lint, debris, or dust stuck inside it. The only solution to this is to clean and adjust them properly.
The quality of the thread is very important in a sewing project, the shredding of lint is caused by the low-quality thread which gets stuck in the machine causing it to get jammed. Also, there are chances for low-quality threads to break easily.
Sewing fabrics consisting of too thick layers can also cause the sewing machine to jam because they are unable to fit under the presser foot. So, make sure that the layers of the fabric are thin enough to fit under the presser foot.
Jamming of the sewing is a normal thing and happens most of the time, so you do not need to worry about it. If you find your sewing machine facing any of these problems, make sure to check it properly and find a solution.