any advice?

[VickyRyan]

I am in my early 50's. I do work-out often and eat fairly healthy (no fast foods, little processed foods, low sugar, etc)  For the past 2-3 years I have had soreness and tiredness in my left arm (comes and goes) more recently over the last year, it is more often than not that it tingles "inside" sometimes sore (when I am still or sitting), and more often than not the top of my whole arm itches (not underneath)... any suggestions?

[ScalpMassager]

The symptoms being in your left arm could be significant (perhaps a precursor of a heart condition imo) -- are you in good cardiovascular health?  (low blood lipids, good one / two / one minus two minute 'heart recovery rate' measurements after high exertion, etc.)

Do routines that help open up your shoulder joint (eg. shoulder rolls) reduce your symptoms?  That might suggest it's merely some form of nerve pinching going on.

[TheLightSeeker]

Peripheral neuropathy should be ruled out first.
Underlying causes should also be investigated, such as kidney dysfunction,
deficiencies like Methylocobalamin, B6 and other deficiencies affecting nerve health, also hypothyroidism, inflammatory conditions etc.

Best wishes,
Niko