Running too many apps at the same time or using the tablet while it's updating software may freeze up the device. Check to see if any unnecessary applications are open or if updates are currently being installed to the device. Short term speed can be improved by either closing these extra apps or simply letting any downloads finish before normal use.
If your tablet is still slow, this may be caused by a processor unsuited to the high demands being placed on it. Trade out the factory installed processor with one rated higher for performance and you will see an increase in speed from your tablet.