If you don't have a case for your phone, you will be able to feel how hot it gets on certain areas or corners after an update. The phone is still running things in the background and for a while after the phone restarts. This will cause lags and gitters if you launch Apps immediately after an update. Best to wait for it to cool down.
If the problem persists later, go in Device Care and either choose Optimise or tap Memory and tap the Clean Now button. I find that a good old fashion reboot tends to fix things.
It is also important to take note of which App or Apps misbehave. Their internal cache may require cleaning and App started from fresh after cleaning.
