Probably a bot. The IP ranges belongs to Amazon
AWS (Amazon) does a lot of things.
https://docs.aws.amazon.com/index.html#lang/en_usEspecially have a look at AWS Elastic IP addresses -
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.htmlAn Elastic IP address is a static IPv4 address designed for dynamic cloud computing. An Elastic IP address is associated with your AWS account. With an Elastic IP address, you can mask the failure of an instance or software by rapidly remapping the address to another instance in your account.