Transition: naptime

[gravy_train]

In my opinion there are 2 ways you can go about it:
1) let him/her cry it out (this is what I now do after months if struggling with a baby who wouldn't nap)
2) you can go into the room but do not pick the child up - just give them them a little hug and lay them back down in bed. Don't talk. You can go in every 5 minutes for the first day, every 10 minutes the next day (or if you want to stick with every 5 minutes for a few days). The idea is to offer reassurance but to not interfere with the child's ability to fall asleep on their own.
When children wake up after 30, 40 minutes it's because they have finished a sleep cycle and are unable to self-soothe themselves back to sleep. The only thing that has worked for me is to let them cry it out. Within 2 weeks the child will be napping. You can also use white noise during naptime to minimize the sounds of crying for the other children and to help soothe the restless sleepers.
Good luck!