have you tried just waiting it out? i have a rlly slow computer (don't buy a mac oops) and usually just waiting 5 or so minutes for shit to load when i first start it up does the trick
mine used to be relatively alright as well but up until a year ago it started deteriorating. just wait it out for about 3-5 minutes and it should be okay. if not then i'm out of ideas EDIT: also try this if you haven't: https://helpx.adobe.com/ca/photoshop/kb/photoshop-slow-lags.html