I have on 21 month old that is a big mattress flipper! I found that this issue was worse when he was still having 2 naps and maybe wasn't as tired at nap time. In the last 2 weeks, I have cut out morning naps in favor of longer morning park visits. So now when we get home and have lunch, he is so tired that right after lunch he passes out quickly with no interest in goofing around...phew!