There are 256 4-letter words starting with P in the ENABLE dictionary — 7% of all 3,903 words at this length. P is a one-point tile, so the value in this list is positional rather than numerical — which of these you can play depends far more on where it fits the board than on what it scores.
The list divides into 11 groups by second letter, the largest being the 46 words with pa. Scanning the right group is faster than reading the whole list, which is why it is broken up below rather than run alphabetically.
If you know more than one letter, this page stops being the fast way to find it. Enter what you have in the unscrambler — the Contains, Starts with and Ends with filters combine, and setting both length fields to 4 narrows this list to the handful your letters actually allow.
All 256 words, by second letter
PA… (46)
paca pace pack pacs pact padi pads page paid paik pail pain pair pale pall palm palp pals paly pams pane pang pans pant papa paps para pard pare park parr pars part pase pash pass past pate path pats paty pave pawl pawn paws pays
PE… (39)
peag peak peal pean pear peas peat pech peck pecs peds peed peek peel peen peep peer pees pegs pehs pein peke pele pelf pelt pend pens pent peon pepo peps peri perk perm pert peso pest pets pews
PF… (2)
pfft pfui
PH… (7)
phat phew phis phiz phon phot phut
PI… (40)
pial pian pias pica pice pick pics pied pier pies pigs pika pike piki pile pili pill pily pima pimp pina pine ping pink pins pint piny pion pipe pips pipy pirn pish piso piss pita pith pits pity pixy
PL… (16)
plan plat play plea pleb pled plew plie plod plop plot plow ploy plug plum plus
PO… (44)
pock poco pods poem poet pogy pois poke poky pole poll polo pols poly pome pomp poms pond pone pong pons pony pood poof pooh pool poon poop poor pope pops pore pork porn port pose posh post posy pots pouf pour pout pows