Citroen Berlingo starter motor problem? ( it has been changed but the problem remains!)

Hello everyone. Right here we go! The old starter motor used to spin in like it should, but then stop asthough it was stuck or something.
Had it replaced the other day and its starting to do the same (not as bad though).It seems asthough everything is fine when the key is turned but you can here it stop spinning and then it starts spinning again! Hope this isn't too confusing. I appreciate any help that you can give. Thanks...