Stop driving on somedays and you'll be good
Is the issue seemingly weather dependent? Wires can be an issue. I'd start with the basic cheap stuff if your not diagnosing anything. Plugs(which youve done),fuel filter, wires.
Intermittent problems are the worst to figure out and you've got to be ready to test things at all times. Especially when the computer doesn't pick up the issue.
I'd suspect a lean condition that's not bad enough to trip anything. This could be caused by a dirty Maf sensor which I've found are pretty common when people start changing to aftermarket filters.