Do you trust your PCP? If so, go to the cardiologist. If you don't trust your PCP, you should look for another one.
I would see a cardio under your circumstances if anything you will feel better knowing you did.
Hi I think your PCP wanting you to see a cardio should be reason enough for you to do so.
shaking on Saturday,
Sinus tachycardia can be caused by a multitude of different conditions, most of them non cardiac. Im not sure the reason your physician wants you to see a cardiologist unless there are some factors that he/she is concerned with that lends the specific etiology to the heart. Overall, a good history and physical will often point to the primary cause of the symptoms. Without being the physician performing this, I cant comment on why he/she thinks you need a cardiologist.
good luck