I like the natural kind of PB. It separates unless stored in the fridge. And, when removed from the fridge, it is often too stiff to spread. So, I put the jar into the microwave oven for about 15 seconds to soften it up. That works okay if the jar is glass, but not so well if the jar is plastic because often, despite my best effort to remove it all, there's a >tiny< scrap of the paper/foil seal still stuck to the rim of the jar, and it makes quite a loud light show in the microwave oven.
So, now I spoon out the PB for my sandwich onto a small plate and heat it there.
So, now I spoon out the PB for my sandwich onto a small plate and heat it there.