lovebird perch sitting

My lovebird has started falling off of his perch. He can stand on it sometimes, but loses his balance. And I've noticed that he has begun to shiver as if he's cold. He's 6 to 7 years old. His appetite has not changed. He continues to eat as before. I have not noticed any weight loss or weight gain. He is still quite the little chirper. I've noticed he tends to sleep more.

He used to fly around the house. He is no longer flying. Previously, when he would be on the floor, he would climb up my pant leg all the way up to my shoulder. Now, when he tries to climb, it's as if he doesn't have the strength and will fall. He tries to use his wings to help him climb.

He likes to hang out in the pocket of my sweatshirt. I've noticed that he is wanting to be in my pockets a lot more.

His eyes look clear. He's not sneezing.

I'm not sending a picture because he looks totally normal.