This is most likely a hormonal behavior. Male cockatiels can go through this just like the females. The males often get this urge to nest and care for something. And he could also be wanting a mate. You mentioned he isn’t hand raised, but is he tame at all? You did say he is let out of his cage at times, so this is good. If he is tame at all, I wouldn’t thing this is loneliness. If he isn’t, then he likely is wanting a companion. However, that doesn’t mean you should rush out and get another cockatiel. A single bird can be happy, even if not hand tame. He likes TV and that offers a type of companionship. And he isn’t kept caged all of the time. Adding another bird could help or they could end up not getting along at all. I would make sure he has plenty of toys to keep him busy, and even a mirror or two. Mirrors are only a problem if a tame bird gets so obsessed that he won’t let you handle him, or with some females, it can cause egg laying if she decides the mirror is a mate. With a male cockatiel, you do not have that worry. So if this goes on, and he doesn’t have a mirror, try giving him one and see what he does. Hormonal behavior is generally seasonal and temporary. If he seems happy otherwise, then you could wait and see if he goes back to normal on his own. When we heat our homes in the winter, this can trigger their hormones, so that may be what happened.
Thank you for asking Lafeber,