I've Been Experiencing Soreness In My Legs Mainly After Brief

I've been experiencing soreness in my legs mainly after brief periods of inactivity. Like sore mucles but it's making mobility difficult until I get loosened up and going. It seems to be worsening over the last few months. Hard to explain but after sitting awhile it's like I just can't get legs to cooperate as they are stiff and painful. Worried about arthritis or muscles weakening. I'm moderately active and not overweight. The fact that this has come on recently and seems to be getting worse is concerning me.