I felt lightheaded, dizzy, short of breath, heart palpitations, and left arm pressure after 1st moderna shot. ekg showed possible left ventricle enlargement but doctor was not concerned. 4 weeks later i am still feeling weak. should i get 2nd shot?

Absolutely get the 2nd shot. However, would check with a Cardiologist to run some tests beforehand. Very (very) rare episodes of heart inflammation (“myocarditis”) after Moderna (and Pfizer) vaccines - more common (but still very rare) after natural Coronavirus infection.

In light of the symptoms, and left ventricular enlargement on an EKG, it would be appropriate to see a cardiologist prior to the 2nd vaccine; it's important to make sure one's blood pressure is normal, and to ensure there's no valve problem to explain the left ventricular enlargement.