During the day while I'm home my cat engages in normal cat behavior, a bit of cuddling, grooming, playing, eating, lots of napping. But as soon as the lights are off and I'm in bed, he spends large portions of the night running around emitting these loud guttural yowling noises. I have to get up multiple times a night, formerly with a spray bottle but now just hearing me coming makes him hide...and start again. This is fairly new behavior since moving into my new apartment in September. I can't sleep! Please help.