NPC's motivations generally involve other NPCs. They want someone else to do something for them, or give them something, or accept something tangible or intangible. So rather making them up one at a time, try creating groups of NPCs (a village, say, or an extended family) and sketch out the those kinds of relationships between them. Describe their Ideals, Bonds and Flaws with reference to other NPCs.
Here are a few that I made up for populating a town in a thread on the old WotC forum.
Jonh Ano (Stats as Commoner)
Jonh is the bartender at the Queen and Dragon Tavern in Cobble Street. He is privy to a great deal of inside knowledge about what goes on in the town but he is trusted by patrons of the tavern to be discrete and will not willingly disclose their confidences. If PCs ask him about town business, he will not admit to knowing anything specific but he will tell them exactly who they need to be talking to and where to find them.
He is a bald-headed man of average height, well-spoken with a deferential manner and of neat and clean appearance. When working, he wears a white apron that is freshly-starched every day.
He greets regular customers by name and welcomes newcomers in proportion to their apparent wealth. Anyone he considers too down-at-heel will be shown the door. If there is any argument, Sergeant Davy and several members of the town watch will instantly arrive, if, indeed, they weren't already there enjoying a quiet drink off-duty.
Jonh dabbles in the arcane and has a wizard's spellbook that was left behind one day last year by a wizard who offered it as deposit on an unpaid wine bill but never returned to reclaim it. He will not part with the book, since it is not really his to give away, but if a passing wizard could successfully teach him a cantrip, he would allow it to be studied for 8 hours. It contains the four 1st-level wizard spells from the Elemental Evil Players Companion: Absorb Elements, Catapult, Ice Knife and Earth Tremor. Teaching Jonh a cantrip is not easy, however, because although Jonh is interested, he has no special talent for it and it will cost the wizard 100 days of downtime at a cost of 1gp per day to achieve it.
Sergeant Davy (Veteran)
A grizzled ex-soldier with a grey moustache and a thousand-yard stare, Davy is second-in-command of the town watch, under Captain Dorthel. "Firm but Fair" might be his motto. It was at his instigation that a soup kitchen for beggars and starving urchins was set up in Slope Alley, behind the Temple. The priesthood approved of his charitable action and various worthy citizens openly pledged to contribute to the cost of running it because it's a clever way of getting the beggars off the streets. Visitors to the town who "come to Sergeant Davy's attention" but who aren't worth putting on trial for anything serious, are likely to be invited to make a donation "for the poor and needy" to demonstrate that they are upright and honest people for whom a few days in jail would be inappropriate. Purely voluntary, of course.
Davy is often to be found in the Queen and Dragon when off-duty. His favourite drink is a type of parsnip brandy known locally as "Wadka". He goes there to relax, not particularly to listen to the conversation, on the basis that the customers there are far above the kind of uncouth and rowdy behaviour that the watch is employed to control in the town.
Davy has suspicions about the activities of two shopkeepers - Rethew Harness and Rosie Potts. He's noticed that they always seem to have plenty of money to spend but that they never seem to actually sell anything. He will pay 50gp from the town treasury for information proving that they are doing something illegal.
Rethew Harness (Bandit)
Rethew was once apprenticed to a leatherworker who made harnesses and other tack for horses and mules. He fled when his master was imprisoned (falsely, according to Rethew) for trading in stolen horses. He reached Lastdown, chanced to meet Rosie Potts and they immediately became soul-mates and partners in crime.
He keeps a small leather shop near the market square, where he offers luxury goods of reasonable quality but at absurdly high prices. His only real customers are men whom his partner Rosie has seduced. If possible, she will inveigle her victims into buying her expensive gifts from his shop; afterwards, she gives the items back to Rethew and they go halves on the take.
Rethew has a certain rough charm but his looks are marred by deep scars across his face that he will not explain to anyone, even to Rosie. He has learnt the arts of seduction from her, however, and is quite capable of bedazzling rich, bored, women who might like a bit of horseplay between the sheets. Then he plays the badger game, with Rosie as his accomplice.
He is not interested in wilderness adventures but may be up for a little burglary or theft in the town, especially in company with Rosie, if he thinks the proceeds are likely to be worth the risk of being caught,
Rosie Potts (Bandit)
Rosie is a flirtatious woman who likes to dress with a certain flamboyance. She is a skilled potter with an artistic flair and she runs a small, rather pretentious gallery called "Rosy Pots", near the market square in Lastdown, where she exhibits some of her handiwork. Ostensibly the pots are for sale but at such ridiculously high prices that you would think no-one would ever buy any. It is all part of an elaborate scam.
Rosie works in a secret partnership with Rethew Harness and they frequent The Knave's Head, watching for strangers. When they spy a likely-looking victim, one or other of them will seduce him or her and then turn the tables and play the badger game. The suitably cowed victim is then made to feel obliged to to buy a pot from the gallery at an exorbitant price. It's all perfectly legal - no money is extorted or stolen, the victim has simply bought a valuable pot.
Rosie has no interest in adventuring in the wilderness but might be persuaded to engage in a little light burglary within the town if it involves deceiving someone, possibly a former victim.
I could post the whole town, but that's not the point. What motivates these NPCs is - other NPCs.
