Two Weeks Ago I Woke Up And My Left Arm

Two weeks ago I woke up and my left arm like where my bicep area like stiffened up where my mobility was very useless like trying to bend it putting on a button down shirt it would not bend and I had to like grab it by the elbow and physically move it towards my neck to put the button in the shirt on the collar it's like weak and no strength in it picking up things very little strength just my left arm it doesn't hurt but it's like embarrassing it like hangs there I can raise it fingers pre flexible did I strain a tendon or muscle or something never had a problem! Before on no medication please help baffled