A cop can follow you for as long as they want to and it will not be considered harassment.
There's no real set time or a set distance in which a police officer or cop following you becomes harassment.
For it to be considered harassment the police would have to be following you without a justified or valid reason or without an investigation.
If police are following you repeatedly without any legal basis, or with the intent to intimidate you then it can be considered harassment.
For example if it's the same police officer that follows you everywhere you go and not just simply following behind you like other vehicles would and the police follow you to your house and are constantly watching you then it can be considered harassment.
There's no actual law though that states that a police officer cannot follow you for a certain period of time.
Police can also follow you if they have any reasonable suspicion that you've committed a crime or if the police are conducting a legitimate investigation.
Although if the police are following you without a valid reason and the following of you is in a persistent pattern, then it can be considered harassment.
Or if the police's actions seem designed to intimidate or control you, then it's another sign of potential harassment.
And any surveillance without a warrant or sufficient justification is also unlawful.
Also a cop or police officer cannot pull you over just to check your license or even your registration unless the cop or police officer has a reasonable suspicion or probable cause to believe that you're actually violating the law.
A cop or police officer cannot randomly stop someone for the sole purpose of checking drivers licenses or registration as doing so is considered unconstitutional.
For a cop or police officer to initiate a traffic stop they have to have reasonable suspicion that you are violating the law or have seen you violating a traffic offense.
Although if someone reported your vehicle as being involved in committing of a crime and the police spot your vehicle and your tag number matches the description the police or cop can pull you over.
But if a police officer or cop knows your license is suspended already and they see you driving the police officer or cop can pull you over then even if you didn't commit any other traffic violations.
The cop or police officer can use their knowledge of your license status being suspended, including the status of your license being obtained through license plate scans or other means as a reasonable suspicion for a traffic stop.
Police have to have reasonable suspicion to perform a traffic stop on you, which means that the police need more than a hunch, but not always necessarily enough evidence for probable cause.
The police have to have a justifiable reason, which is reasonable suspicion or probable cause to make a stop on a vehicle which means that the police have to have specific and articulable facts that when taken together with rational interference's from these facts, lead the police to reasonably suspect that a crime has been committed or is being committed or about to be committed.
Random traffic stops without any probable cause or reasonable suspicion or often illegal.
If the police or cop knows that your license is suspended such as through a license plate check or from a previous interaction with you and they see you driving then that alone can be the basis for reasonable suspicion which allows the police to pull you over.
Driving with a suspended license is a violation of the law and can result in jail time, fines and further suspension of your drivers license.
The police may also impound the vehicle if it's registered to you and you have a suspended drivers license.
Driving on a suspended license will get you arrested if caught but driving on an expired license which is different may just get you a ticket or a warning.