Yes, some oscillation is normal, but, of course, too much is very bad! Check that the rudder has no freeplay. If there has been previous firewall damage, rudder rigging is more difficult, and they can be a bit loose, this would enhance oscillation. And, check that there is no freeplay in the elevator. Otherwise, unless something appears unairworthy, don't worry too much about it (and don't look back during stalls!)