My parents have never shown much PDA?

What's PDA? Nobody shows anybody affection anymore. Plus, your parents are used to each other, so they probably just got bored with each other. Or, it might be that they are keeping you from seeing them show affection to each other because, one, you're their child, and two, you're a minor. Or, they realized that affection is not the only way to show their love for each other, because they got more mature, and their relationship got stronger. Also, if the snoring is keeping your mother up at night, sleeping in a different room is understandable.