my macbook air reboots when it is closed

Kernel Panic summary:

panic(cpu 0 caller 0xfffffe00240caa28): DCP PANIC - ASSERT!AppleDCPDPTXPowerController.cpp:538 No device added after powering on the rails.

This indicates an issue with a connected display or perhaps a dock with a display connection (whether any actual display is connected to it). Try disconnecting all external devices to see if that stops these Kernel Panics.

DCP == Display Co-Processor

AppleDCPDPTXPowerController seems to reference the Display Co-Processor Display Port Transmission PowerController

It seems that power was activated, but no device was connected.

Also, the Spotlightknowledged process had high CPU usage......this has something to do with Spotlight indexing, but I'm not sure exactly what this exact process does.

FYI, a VPN does not provide the privacy or security you may think it does. A VPN only provides security & privacy when accessing an employer's network by connecting to the employer's Firewall/VPN server.

I hope you have a good backup. There are a lot more new ways to permanently lose access to the data stored on the internal SSD with the recent Macs due to all the hardware, software, and security changes. People should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data.

You neglected to provide any useful details such as exact model of the Mac & version of macOS involved. Run the third party app EtreCheck and post the complete report here so we can examine it for clues.

You may also want to review the following article as well:

Writing an effective Apple Support Communities question - Apple Community