2002 Nissan Altima Random Misfires

2002 Nissan Altima, 85k miles. Lately, about every few weeks, I get a misfire on cylinder 1 on a cold start. After a few seconds, it smooths itself out and operates normally. This morning, the same happened, but it was cylinder 3 instead (I use a smartphone OBD2 reader. Not sure if it matters, but the exhaust manifold/precat was replaced about 1k miles ago (to avoid the infamous pre-cat failure in this year model)

This car has been great! What the heck? lol

P0300 2002 NISSAN ALTIMA SEDAN Code Cylinder Misfire Detected Random Cylinders (autocodes.com)

Misfire Due to Faulty Intake Manifold : Nissan Altima Engine (repairpal.com)

Except it didnt throw out P0300, it threw out P0301 and then P0303 on separate days. Or does that make a difference?

po301 is for cylinder 1 misfire and po303 is for cylinder 3 misfire

Yes I realize that. I guess what I am asking is what could cause a misfire on two separate cylinders on two separate occasions? And in both cases, the car smoothes out after a few seconds and operates normally.