Why after the gym my arms feel like they restricted from blood flow?

Perhaps... The most common causes may include: a) your highest rib may be rubbing against the arm blood vessels b) you may have an abnormality of your aortic arch which restricts blood flow c) over exertion can cause swelling within your muscles which in rare causes can restrict normal blood flow. D) chronic blood clots could also contribute. If it keeps happening, see your doctor and share these ideas.
Thoracic outlet. Muscles at base of neck can constrict arteries and veins. Have doctor check you for thoracic outlet syndrome.