Greetings jwn7882,
The issue you are describing does sound odd. If the camera is sitting in idle but in the on position, and the power saving feature is enabled, then let's press down on the shutter button halfway to see if this wakes up the camera. If the camera is powered off and then you switch it back on after it's been in idle, but the camera is not powering on, then let's see if resetting the camera will resolve the issue. You may click on the following link to view steps on how to reset the EOS R3 camera.
https://cam.start.canon/en/C010/manual/html/UG-07_Set-up_0300.html
I would also suggest removing any attached accessories that may be connected to the camera when this issue occurs. For example, remove any cables or cords, remove any wireless transmitter or flash that maybe connected to the top of the camera. If possible, test to see if this issue occurs with multiple lenses as well as different memory cards. This may help to determine if an external device or accessory is the root cause of the issue on why the camera is not powering on.
If the issue persists, then the next step is to suggest on sending the EOS R3 camera to our facility for service. Items purchased directly from Canon USA or from an Authorized Canon Dealer do include a one-year warranty if the item was purchased less than a year ago. You may view a list of Authorized Canon Dealers by clicking on the following link. I would recommend including a copy of your Proof of Purchase when sending in your item for the facility to review for any in-warranty service or repair.
https://www.usa.canon.com/internet/portal/us/home/contactus/where-to-buy/authorized-dealers
Canon U.S.A., Inc. has created a new online repair portal that allows you to set up service in a few simple steps. The repair portal gives you the ability to set up service for multiple pieces of equipment at once, and to receive a repair estimate in the majority of cases, depending on your model and issue. The portal also allows you to upload images or videos that will assist us in repairing your product. You can also select how you wish to be notified of the progress of your repair. The portal's service history section allows you to view all services that have been performed on any of your camera or video products since January 7, 2020.
Please follow the link below to access our online repair portal to arrange for service:
https://mycanon.usa.canon.com/signin
Instructions for Accessing and Using the Online Repair Portal.
You will need to access or create your My Canon Account.
If you already have a My Canon Account and your product is already registered, simply click on the “Get Repair Services” link on the left menu and follow the onscreen instructions to arrange for service for your product.
If you have a My Canon Account and your product is not registered, you must register your product first. Click on the “Get Repair Services” link on the left menu, then click on the “Register Product” link on the right. After your product is registered, click on the “Get Repair Service” link on the left menu and follow the onscreen instructions to arrange for service for your product.
If you do not have a My Canon Account, you will need to create one. After you create your account, click on the “Add Product” link to register your first product. After your product is registered, click on the “Get Repair Service” link on the left menu and follow the onscreen instructions to arrange for service for your product.
Once you have completed the repair request, you will have an opportunity to print a copy of the request for your records. This request form will also contain shipping instructions and an address label that you will attach to the outside of your shipping box when mailing your equipment for repair.
