3.5 month old play time

My son is 3 and a half months old, and his play time consists of laying on his back or sitting against the couch listening to music kicking and smiling. I'm glad he's happy! However it worries me that he doesn't want anything to do with his toys like he won't reach for them. He occasionally likes his play mat and hits the toys hanging from it or he'll just lay on it listening to the tunes it plays chewing on his fingers (he's also teething). Stupid question but is this normal? How will he develop his teaching and grabbing if he doesnt want his toys?