Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.
If you google shaking hands or tremors a ton of stuff comes up so there's lots of possibilities.
I did a search on "shaking right hand" and you are right: it could be caused by several things. The thing that concerns me most is that my tremor occurs while my hand is at rest, which is a specific symptom of Parkinson's, and that is something I REALLY do not care to think about at this point!
I haven't noticed it today, so am hoping it was just a fluke.