Mid-afternoon meltdowns. Super-short naps. Clinginess around-the-clock. Sound like your child? The problem (and, actually, the solution) could be sleep — and you’re not the only parent struggling with the issue: A whopping 37 percent of children between the ages of 4 months and 5 years are not getting enough shut-eye, according to the CDC’s National Survey of Children’s Health. Not only does this make for cranky kiddos, but chronic lack of sleep can lead to…