Pleco help- on his back?

[Buddyboy]

I have a pleco that's about 7 years old in my 15G tank. I have seen him do the same thing on many occasions. Like he is in a trance like state, doing that gulping thing that plecos do. hehe The pleco only does this on occasion and still looks healthy to me. Is he eating well? If so, I don't think you have much to worry about!