A cop can pull you over if they have no lights as long as the cop has probable cause to believe you've committed a violation.
The cop can legally hide to observe any traffic violations and the cop doesn't need to announce their presence before they initiate the stop.
This is not considered entrapment, as entrapment involves the police inducing you to commit a crime that you wouldn't have otherwise.
Although without the police car having flashing lights, it's often highly frowned upon.
Most times though the police may hide without lights and only light you up when they get behind you.
If you're pulled over without lights, pull over safely in a well lit area if possible like a gas station or a fast food parking lot, if you can't pull over in a well lit area, continue driving at the speed limit and put your flashers on to indicate you acknowledge the officer and pull over as quickly as possible.
If the police car is not marked, you can call 911 and let them know where you're at and confirm that it's an actual police officer pulling you over.
Cops also don't have to have their headlights on at night and cops can also legally hide with their headlights off and they can pull you over for violating laws, even though they are doing the same thing.
As long as the cop or police have reasonable suspicion of some regulatory violation or traffic violation, like a blown headlight or taillights, turn signal lights etc being out, the cop or police can pull you over.
The initial stop is often considered a low level stop, but it also gives the cop, the opportunity to look for other more serious violations like open containers or expired registration.
The officer also has discretion in how they handle the traffic stop, and it often comes down to the officer's judgement at the moment.