Is going limp like a rag doll a normal behavior for an Alzheimer’s patient?

Is it normal for someone with alzheimers to have an episode where he just goes limp like a rag doll? My dad was fine, then all of a sudden, he want s6o remove his pants like he was ready to go to bed, It was time to eat so we helped him to the table to eat, then all of a sudden he goes limp on us. He is like a rag doll. All we got from him was an uttering of yea, yea, yea, I do not know if he was trying to answer our questions or not. We helped him up and put his walker in front of him, he would not walk for us. As long as the walker was moving, he shuffled along. When the walker stopped, he did as well. Could not get him to move without the walker moving. We finally go to his bed and layed him down. He continued with the uttering. We let him rest, I kept going back to check on him. He was uttering , la, la la.... I think I he wanted his light out. Once I turned the light out he was quite. I checked on him later and he was talking the usual rantings that would normally do. Whatever was happening, it was past. Has anyone experienced this? Do you know what was happening???