tingling in arm

For the past month I have had spontaneous tingling in my left arm several times a day.  Rarely in my right arm.
Had a thyroidectomy 15 years  ago.......cancerous...... take Synthroid daily and visit my endocrinologist annually.
Otherwise healthy at 72 years of age.  I work out and eat well.  Read prodigiously, but when I forget something, I have concerns......maybe unrealistic, don't know.
What could be causing the tingling in my left arm at any time of the day for no known reason?

Thank you