Only if your abdominal area is not strong enough. Make that strong and the weight pressed overhead will never be heavy enough to hurt your back, assuming proper form is employed.
I imagine the shoulder press machine has a backbench so that you don't need to do your own stabilization. You'll likely have to reduce the amount of weight you use for your presses at home since the midsection is not in condition to handle the poundages used on the machine.
The weight has to be further reduced since the stabilizers in the shoulder girdle have to work harder as well to keep you in the lifting groove. The tendency is to lean back in these cases to bring the upper pectorals into play. Lean too far back, and you can hurt your back due to inadequate strength in the midsection. Best to lean back as little as possible.
Overhead lifting is best done standing, not seated. It's darn good ab training, too.