Are premature ventricular contractions normal if infrequent? And do they often times go unfelt?

Common. They are common, never normal altho typically benign. And yes, they can go undetected many times.
Often normal. Almost everyone gets a few premature ventricular contractions (PVC's) every day. They are often unnoticed. It takes several thousand PVC's per day before there's any concern of leading to heart damage. Rarely, PVC's can be a sign of underlying heart conditions, so if you're concerned, or have chest pain, dizziness, shortness of breath, then see your doctor for reassurance.
PVCs. Some runners have pvcs, have healthy hearts. Some with healthy hearts have symptoms with pvcs, and decide to use medication. Patients with unhealthy hearts, by blocked arteries, by muscle damage, or by electrical problems, and have pvcs, can be at increased risk for serious heart issues and need cardiology care. An ECG or holter monitor will test for pvcs and other heart rhythm issues.
Palpitations normal. The short answer is yes and yes! everyone gets occaissional missed beats or premature ventricular contractions, and if they are scattered and just a few, it is not a problem. If they are really annoying, a small dose of a beta blocker might relieve your symptoms. The only time premature ventricular contractions are dangerous is when they are coupled together and become ventricular fibrilation.