The style guide used by The Economist (quoted here) suggests that hyphenation be used to avoid ambiguities.
If "switching off" in a sentence introduces an ambiguity, it can't hurt to use it.
Here is an example with no ambiguity:
Switching off the light would be a good idea now.
Here is one with some ambiguity:
I think your switching off of the light would be a good idea now.
Most likely you are suggesting that someone turn the light off, but switching could could conceivably mean something else not associated with the preposition following.
The meaning is clear with a hyphen:
I think your switching-off of the light would be a good idea now.
