Did you ever find the cause? I am experiencing this as well. It comes in flares. It was just the left temple 10 months ago. Now it’s both temples and above my right ear. It feels like something is inside tapping as if you would tap someone on the shoulder. It is pain free. I do have some neck pain that came on at the same time. Trigger warning. In September I was found to have 2 brain aneurysms. My symotoms haven’t gone away since fixing the big one but they are less severe. I have had CTA, MRA, MRI and angiograms. None of these things have shown an issue it could be. I just had a transcranial Doppler done on a day that I was not having the thumps but last night diagnosis hit my chart as “mild mca spasms on right side”. I’m not sure what will happen from here but your post is the only one I’ve found that has described pain free thumping like I have. Sometimes I have a sensation in my left ear that is also not my heart beat. Don’t give up. I would ask the doctor to refer you to a neurologist.