Toddler obsessed with wheels

My son is just over a year and a half old and is obsessed with anything that has wheels.

He reaches for the wheel under the fridge and lays on the floor and spins it, in his stroller he tries to lean over to watch the stroller wheels spin, and he flips his vehicle toys over and spins the wheels.

He also loves to stack his toys. He puts everything on top of each other, no matter what it is.

I’m just worried it’s an early sign of autism. He can’t talk yet, can’t point or wave, and sometimes rocks and flaps his arms, but not constantly. His doctor says it’s too early to tell but I went ahead and made an appointment with a specialist which has a year waiting list.

Have no idea on his social skills as he’s never been to daycare yet and hasn’t been around other children.

Just curious on people’s thoughts as I have no idea what’s considered normal or abnormal behaviour.