This can be due to the heat generated by either or both the drive and the total system. If the system where the drive is installed in is running pretty hot (or badly cooled), drives warm up as well. Especially if they are mounted in the upper part of the case (because heat goes up).
To check wether it's the system or just the drive that's running hot, you can take the drive out of the system and use it lying on the table. If the temp is about the same, it's the drive that runs hot. Otherwhise, it must be the system. Additional cooling (casefans) may solve your issue.