Re: [PC] Extreme Start Up Lag In Mass Effect
The only thing I can think of is maybe a corrupted game-profile of the nvidia driver. You could try downloading nvidia inspector and optimize your settings according to this guide ("advanced tweaking"). You should first try to reset every setting shown under the Mass Effect 3 profile.
[edit]I found this regarding lag in ME2. Not sure if it'll help, but surely worth a try, should be the same procedure for ME3. Some people could set the affinity back to all cores after confirming the affinity to one core as well and ME would still run smoothly.