Thanks for the post.
I have never encountered someone who described this symtom set with sertraline (Zoloft), but sertraline is not infrequently associated with anxiety, fatigue, nervousness, diarrhea, insomnia, and a few others. These symptoms are all likely related to higher levels of serotonin associated with taking sertraline, and point to altered autonomic nervous activity. Altered autonomic nervous activity could potentially lead to higher levels of heart rate during exercise, thus a link between sertraline use and tachycardia could be possible.
Tachycardia has been reported in users of sertraline who developed (1) serotonin syndrome (either from concomitant ingestion of other drugs or overdose of sertraline), or (2) AVNRT (an arrthymia also associated with concomitant ingestion of other drugs, particularly stimulants).
I can't advise you as to whether or not it is safe to continue to exercise with the limited information you provided. A general guideline would be that if your symptoms have been stable for a long period of time, then it is likely safe to continue at a reasonable exercise pace. If on the other hand, your symptoms have been progressing, then it might be wise to hold off exercising until seen by your doctor.
One last thing which I hope does not apply to you. I have seen some women runners, who also happened to be on anti-depressants, who suffered from bulimia or anorexia nervosa. They experienced increasing fatigue due to caloric restriction and electrolyte imbalance.
Hope that helps.