I usually can't move off the spot after combat. Why is this and is there any way around it?

It's like this in Kotor 1 too. Just wait a few seconds, try to click on any nearby containers or keep pressing a movement key until you finally can move.

That only seems to work sometimes but thanks anyway.

The following method reliably worked for me:
Press the "move forward" key and, while keeping it pressed, press the quicksave key. After the game has been saved you can move again.