Your Ultimate Backup can get warm to the touch during use, especially when backing up lots of files at once. This is normal and expected — it's most noticeable when using the USB-C or USB-A ports on the drive, as these allow for high-speed transfers of data.
However, a drive should never get too hot to touch comfortably. If your drive becomes uncomfortably hot, disconnect it and allow it to cool down, then report the issue to one of our live support agents so we can determine whether something is wrong with your drive.