Intermittent low fps issue on PC, goes away after restart?

I spent much of my first run through of Inquisition trying to tweak game/origin/pc settings in order to get this game to run smoothly and without crashing. I've found that I can eliminate a lot of my problems simply by playing in offline mode, and now, in my second run-through, the game is playing smoother than before, probably thanks to an update from Bioware as well, but I'm still being troubled by a nagging problem. About half of the time, my game hums smoothly along at about 60 fps, and I am no longer suffering any killer fps drops or frequent nvidia crashing, however, the other half of the time, my game will run at about half that, closer to 30 fps, which makes the game unbearable. I haven't been able to narrow down why this happens, as far as I can tell, everything is exactly the same across both modes.

I do think I have located a tedious way of ensuring the game runs smoothly, which is to RESTART my computer before I begin playing. I have never had issues this way. If I try to start the game under other circumstances, it will often end up slow/laggy. Even when I initially start my computer after having it powered off for a while and try to play DAI, it doesn't typically give me the full fps levels I want. Restarting is the only repeatable process I have found with a 100% success rate. This isn't a huge deal, (though I wish now that I had a SSD), but I was wondering if anyone knew of a reason why this issue would keep popping up and whether there was a much easier process that could circumvent it?

My PC:
Core i7 4790K 4GHz
GTX 760
16 GB Ram

Many thanks!