Sleep training

Dear parents Can I check how soon you sleep train your child to sleep in their own room? My son is 2 years old, and we are kind of ready to train him as he usually sleeps thru the night. However, there are nights when he doesn't, and he will cry murder. So we didn't know if we should proceed to let him sleep alone or wait until his sleep is more regulated like ours, maybe 4 years old? Share your thoughts please or tips. :)