I get a heavy numb sensation in my right arm and leg intermittently. it doesnt seem to be caused by lying/sitting positions but comes and goes. what could this be? thank you?

Could be perhaps 100 possibilities. Need much more detail. I would not drive or operate machinery until cause is established. Your body is talking to you. Listen and take good notes and keep a diary: what brings it on, where does it go, what can you do to stop it. etc. You and your Dr will figure it out.

To experience recurrent numbness simultaneously in your arm and leg raises a question of pathology in or affecting the left cerebral cortex. At your age multiple sclerosis comes to mind. I recommend consulting a neurologist directly for accurate, timely diagnosis and appropriate testing.