My 3 1/2 month old, whose never really had nightime sleeping issues, was put to bed tonight at 7pm. All of a sudden at 8:30pm, he wakes up all bright eyed, happy, laughing, and kicking with joy. Now at 9:30pm he shows no signs of slowing down or being ready for bed. What's going on with him? Will he eventually tire out and be ready for bed? Is this the start of the sleep regression?