
As the book of the bitch says, the digging and panting is often termed as stage one, the deep sleeping is the pups on the travel classed as stage 2, a little shaken often happens just after this although not always. It can take 48 hours from the real rapid digging till pups appear.
As previously discussed on other threads ( may be worth a search) the temperature drop is often a good indicator of labour starting if taken several days before and charted properly. It has been the best method for me. My bitch had puppies Wednesday night and again the temp drop was indicative of a soon to be litter, they arrived 12-14 hours after the drop.