Your tablet gets its position from a combination of GPS reception and clever trickery by Google involving what wifi signals your tablet can sense. (Some phones add an additional level of tech trickery that includes cell signal information in the process.)
An actual GPS fix is more accurate than a wifi-based fix, so if available that's usually the way your location is determined, and wifi is used as a fallback. But indoors, GPS reception can be difficult to acquire or maintain. Even when an adequate GPS signal is acquired, altitude is more sensitive to error than lat/long, so if your reception is marginal, your altitude fix will be noisier than your lat/long fix.
If your GPS reception is going in and out, then your tablet will be shifting between GPS-based location and wifi-based location, which can cause "jumps" in your location fix.
All that is to say that while your tablet is not actually moving, the data it uses to determine its position may be varying such that it thinks it's moving, especially indoors where it probably can't maintain a strong GPS signal.
Finally, when iFly is running it prevents the tablet from going into sleep mode. You should always close the iFly app when you're done using it.