Muscle spasms or twitching on my chest/abdominals.?

so every so often i get these random muscle spasms or twitches. they dont hurt or cause any problems but i can notice my skin moving and feel the spasms when there happening. sometimes itll be one of my legs or arms or itll be my stomache/chest. at the moment its doing it on the middle left side of my chest. not by my heart or anything. but like the top middle of my rib cage. im just wondering if anyone knows what this could be. thanks for any help you can give me.