Cisco 4500 switch rebooted itself

[ปลาวาฬทราย RMUTT CPE IX]

I have a Cisco 4500 chassis.  It is on a known good UPS, has redundant power supplies and everything.  A moment ago, the switch restarted itself for no known reason.  I couldn't find anything out of the ordinary ... it just came back online by the time I got to the switch room.

I went into the IOS and did a sh hardware and got this:
ROM: 15.1(1r)SG6
ph-4500 uptime is 48 minutes
System returned to ROM by reload
System restarted at 15:02:46 CDT Wed Mar 24 2021
System image file is "bootflash:/cat4500es8-universalk9.SPA.03.09.00.E.152-5.E.bin"
Jawa Revision 4, RadTrooper Revision 0x0.0x41, Conan Revision 0x378D

Last reload reason: reload

My question is, what else can I do from a troubleshooting standpoint? No one else has access to the switch to reload it so I can only assume it lost power for some reason and "reload" is just a generic reason.  Is there a different "Last reload reason" message if it just loses power?

Any pointers on figuring out what happened?

Thank you very much.

[Leo Laohoo]

CSCux43406

[Mark Elsen]

 - Compare the reload reason as being provided by show version , as to figure out what happened could be clarified if for instance a syslog-server was used, and an snmp-trap receiver, if not. Then configure those for further troubleshooting and device monitoring.

 M.

[Leo Laohoo]

Post the complete output to the following commands: 

dir crashinfo:
sh log on uptime detail