First, how often is it happening? Is it every few seconds? or is it when you just don't touch it for a short while. If it is the latter, then I would check your time out settings. If it is the former, then I would try starting up the tablet in "Safe Mode" and see if it happens in there. If it doens't happen in "Safe Mode" then you have an app, virus, malware, etc. on the tablet that needs to be removed to resolve the problem. However, if it does happen in "Safe Mode" then I would have a tech look at it.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.