Ive never seen this alarm before, but it looks like an environmental alarm that the switch processor is detecting.
If an overheating condition is detected by a certain module (in your case, the switch processor on the Supervisor module) and it is not rectified within a certain timeframe, the module will go into red alarm and shutdown. If your SUP is shutting down and you have no redundancy, that would explain why the switch reboots.
If the switch is new, I would definitely open a TAC case with Cisco and provide them thd output of the alarm in the ticket itself.
Meanwhile, do yourself a favor and check if the fans are operating normally and if you have good airflow around the switch and the cabinet it is mounted in.
Also, check out this URL for installation instructions regarding airflow and temp.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...