My android apps is lagging because some of my running apps like android system is restarting

[Rendell Sibal]

My lenovo tab android lollipop is lagging from the messenger. I see the running apps some of them restarting. Why this happen?

 

[B. Diddy]

It is normal for the system to automatically open apps into RAM. Android prefers to keep RAM relatively full. If you try to force close apps, the apps will either restart, or the system will open some other app to take their place.

There's probably some other reason why things are lagging. Can you give more details? What do you mean that it's "lagging from the messenger"? And what is the exact model of your Lenovo tablet?