The process com.android system has stopped

In my experience this typically happens when there are more apps/processes than the device can handle running all at the same time. It happens on my Lenovo tablet and the cheaper Android device I bought recently. Sometimes it only affects certain processes when I'm playing certain games or if there are too many things all open and running in the background. It may help to go into apps in settings and just go down the list and force close any games, apps you aren't using and see if this helps. Unfortunately I find it's only a temporary band-aid solution as certain tasks just need more power/memory to function properly and less expensive devices sometimes just fall below the requirements.

Where are you seeing those messages pop up and was it having any other symptoms before you started seeing the messages?

Try these steps:

After your tablet turned off, hold Volume Up + Power buttons at the same time for about 5-10 seconds. You will see options. Use Volume down button to scroll and select Wipe data / Factory Reset.