iMac started booting on it's own

My iMac with Sierra 10.12.6 has started booting up on it's own in the morning and it's not something I have it set to do. The energy saver panel is not set on a schedule. This has been happening (I think) for a long time but I didn't realize it because the time it does it is at a time the computer would normally already be on. Since it's the holidays and I've been busy, I have not been turning on my computer at 5:30am as usual and have been coming into my office at 6am and then it's already on. The past 2 days it has spontaneously started up on it's own at 5:54am. At first I thought it was having an error at shutdown and not shutting down, and that I just didn't catch it so it stayed on all night, but last night I made 100% sure it was shut down and rechecked it a few hours after shutting down to make sure. I came in late again this morning at 6am and it was already on. I checked the console system log and it shows the sequence of shutdown and startup for the last two days -- keep in mind that the boot time is NOT initiated by me:

Dec 8 16:29:18 Macintosh-HD-3 shutdown[9500]: SHUTDOWN_TIME: 1512772158 298924

Dec 8 16:29:18 Macintosh-HD-3 com.apple.xpc.launchd[1] (com.apple.xpc.launchd.domain.system): System shutdown initiated by: shutdown.9500<-sessionlogoutd.9497<-launchd.1

Dec 9 05:54:52 localhost bootlog[0]: BOOT_TIME 1512820492 0

Dec 9 18:43:10 Macintosh-HD-3 shutdown[12291]: SHUTDOWN_TIME: 1512866590 864511

Dec 9 18:43:10 Macintosh-HD-3 com.apple.xpc.launchd[1] (com.apple.xpc.launchd.domain.system): System shutdown initiated by: shutdown.12291<-sessionlogoutd.12287<-launchd.1

Dec 10 05:54:52 localhost bootlog[0]: BOOT_TIME 1512906892 0

It shows that I did shut down the computer. There have been many times over the past few years when we traveled that I would find my computer on when we got home and I could not figure out how that happened. Now I believe that this has been happening for a long time and I didn't know it only because I usually turn on my computer before it would do this on it's own. I have also had an ongoing problem with it periodically popping a message up late morning saying the computer is scheduled to go to sleep (IT IS NOT) and I have to cancel it. That has not happened for awhile but it carried over from my previous computer to this newer one less than a year ago. If anyone know why this might be happening let me know. thanks.