Was this a phone software update or an app update @irfanpatel
I'm using Version 15.43.32 YouTube App and on the September update and experiencing no lag.
You could try clearing the cache and if necessary data in the app via settings, apps, YouTube, storage, clear cache / data.
Current Phone > Samsung Z Fold³ 5G.
Mine has been doing the same exact thing since I updated my phone for the last update if Im in YouTube or YouTube TV it goes into a jittery lag while using it if I've been using it for a while to the point I have to restart my phone
Same for me, happening since last 6 months. Such a garbage experience after spending 1300 dollars. Feels like throwing away this sh***y phone.