After Having Having Lunch Last Evening, Sit Back In Chair

After having having lunch last evening, sit back in chair and went off to sleep, woke approx. 30 minutes later
andmy left arm was asleep. It felt heavy and yes I could move it up and down, but it had a rubber type feeling, just clumsy to hold anything in it and rather difficult getting it into my left pant pocket. After about 15 minutes, it started to feel better. I normally walk my dog a lot in the day and he pulls on my left arm a lot. It does have abit of tingling in it. But I have full functions of it. what do you feel could be causing this.