At nap time, many times, I carry my daughter(8wks) in an up-right carrier (she recently vetoed the sling) and she often nods off for nap. But when I put her down in bed she is up within 20 min. Or she just kicks and whines until I take her out. In her swing she sleeps and doesn't wake up. Do you think these cues sound like she "prefers" the swing?