My Yorkie's odd behavior...?

My 2 year old Yorkie recently has begun to scratch the area around where she plans to sleep. A friend once told me that this was because of an innate behavior pattern that Yorkies have-the reason being that they are "checking for snakes" before they lay down. Is this true? I mean, surely I don't have any snakes in the couch or in my bed?! If you know the real reason why she is doing this, please explain! Thank you!