Look in your wheel arch, at the top of the tyre you'll see the bottom of the spring, which is sitting on a pressed metal pan. Under that pan, between the pan and the lower leg of the strut, is a bearing. On many alfa's (sud/sprint/33/164 + others) the spring doesn't swivel with the strut when the steering is turned (more typical is for the spring to swivel with the strut). The bearing allows this.
Anyway, these bearings like to fill up with dust and rubbish and then they fail. Your S2 33 should have ball bearings within a yellow plastic housing. When they fail you can often see bits of the yellow plastic housing making a bid for freedom from under the spring pan (if you clean all the muck off the area). A quick test is to reach in with both arms and grab each side of the lower pan and try to swivel it. It should turn freely and smoothly but with a fair amount of force as you're winding up the coil spring. You won't be able to turn it far. If it's grindy or sticky or jumpy to turn then your bearing needs replacing.
To do that, remove the strut and apply spring compressors to the coil sping. Remove the top nut, top mount assembly, and coil spring and the lower pan will just lift off too. There is your bearing - replace and reassemble.