Could be failing ignition system component , or weak fuel pump , or clogged exhaust or failing mass air flow meter , or intake air hose leak , or fouled spark plugs , or blown head gasket or transmission torque-converter lock-up solenoid switch is stuck.
RepairPal Certified shops can diagnose and repair your 1996 Mercury Villager. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Or any number of things.......etc.