Groaning noise

Hi, I am hearing a really strange “groaning” or grunt noise right after the engine turns over. The colder is the louder it is. It only lasts about a second. It’s only when the engine is cold. Any clues?

Is the groaning only while the starter motor is actually working? Many times when starters start to go…the bearings will groan while the starter is in motion…if you had the starter off the car and hooked it up to 12v and made it turn on…sometimes they SCREAM and wail…a horrible sound but when its attached to the flywheel the noise is changed…could just be the bearings inside the starter?

Also it could be thatthe starter gear is unable to withdraw itself from the flywheel and thus get spun by the spinning engine…and will wail just the same due to the bearings inside the starter. My guess.