When the refrigerator close function is working, the door will pretty much close by itself. However, you may sometimes find that you have to press on the door for it to engage and feel closed.
Even then, it feels as though it is not “engaging” as it should. The suction that keeps the door properly closed is absent and it opens extremely easily. You should start by checking whether the door has become lop-sided or the hinge on the door is faulty or needs adjustment.
The seal may also be faulty, or it may not be possible to seal completely.
Some models of refrigerator have a transparent heel on the seal to prevent it from sealing too much. If there is one, you could try removing it.
The problem may also be that a temperature sensor for monitoring the temperature has been fitted in such a way that the lead to the sensor prevents a perfect seal. Try to fit the sensor through the existing opening and seal from the outside using permagum.