Left Arm tightness revisted

I'm 40, riding about 100 miles a week and overweight.

I made post here long ago about left arm tightness I was feeling when I started working out. So I hop on my bike, and 10 minutes in I'm at 130 bpm and the following symptoms occur.

Shortness of breath,
Dry mouth
Tightness in my left arm, as if I have a turnoquit applied. Wouldn't describe it as pain, just strain.
Percieved Effort is 9-10
HR indicates I'm barely working hard.

This will continue for anywhere from 15 minutes to an hour, but it goes away. It may return later more mildly If I'm pushing myself into 170 HR

After my last post I was strongly urged to go to doctor, and I eventually did. Got a stress test and blood work. Everything was fine, cartiologist was bored with the procedure and gave me about 15 seconds of his time only to tell me I had a good heart. During the test I felt fine as my HR got up into 150s. This was 5 months ago.

I never heard anything else from the doctor.

Tends to be worst late in the day, especially after work. Usually far more mild if I'm not working.

Any ideas, and I really don't want to go back to doctor, haven't paid for the waste of time stress test yet.