Change any protocol relative link, those starting with just // to a regular http:// version. DW has massive problems with that particular link style (a known issue to Adobe). If you don't use https for any of your pages, there's no need to use the protocol relative link and you can change the // to http:// permanently.
Issues with third party servers can cause DW to go nuts from time to time. If you don't have any protocol relative links, but you do have links to external sites in your <head> section for scripts and the like, try commenting them out by wrapping them in html comments one at a time to see if there is one in particular that is causing problems for you.
If you find one that is the driving force for the lag, make a copy of it and save it into your local site, then link to that local version instead.