Replaced bag and started to vacuum, it got VERY loud and then shut off after a few minutes. What is wrong? I tried it again, and did same thing. Never did this before.

Check all the tubes from behind the brush all the way to the bag. The 'Bag Full' light just detects a reduced air flow by the increased air pressure..

When the light blinks and the unit shuts down it most likely needs to have its bag changed. You may find tha the bag is not up to the fill line, but is likely over a half. Our experience is to change the bag and the problem resolves.

Is the motor overheating? Or is it more like there's a loose connection in the on/off switch? What happens if you reel in the cord a little? Could be there is a spot somewhere in the rings which is corroded or worn out and not making contact. Might also be a break somewhere in the winding inside the motor.

I have a similar situation in my Aerus C15C3. An Aerus brand bag ruptured inside my vacuum cleaner, but I didn't realize until the motor started making a horrible noise! To make matters worse, I hooked up my older Electrolux LE 1623 and at tried to suck as much debris out of the air intake at the bottom of the bag compartment, and then put the C15C3 back into service. I should have stopped then and there and started working on trying to get the motor and the fan out of the housing. But my machine was overheating and shutting off.

Sears Parts Direct has diagrams of the Electrolux LE 1623 on their website. The good thing about Aerus and the old Electrolux-USA is that they all have similarities in their design, but Aerus does like to tweak their design just enough to foil or at least complicate access to DIYers and general vacuum repair shops.

I hope you post what you find out!

Similar to your Kenmore upright is the canister. Here is a video clip by another with similar issue of trying to open the darn thing up. I hope this gets you closer to solving your problem with the vacuum. If not with a few Kenmore vacuum "search" in youtube I think you will find what you need.
PEACE
https://www.youtube.com/watch?v=s0aaoPzCAcM Kenmore 116 26212690 vacuum cleaner disassembly to motor

Bad on/off switch? Possible contact problem inside the cord reel?

Take the filters out and turn the vacuum on, if it will stay running without the filters in it you need to replace the filters. Filters should be replaced every few months. Clogged filters still pick up some dirt but miss a lot plus it causes the motor to run hot which will cause damage to the motor reducing it's life.

THE PROBLEM SEAMS TO BE WITH THE THICKNESS OF THE CARPET AND THE PAD-ALL VACUUMS NEED TO BE ABLE TO BREATHE IF THE PAD AND THE CARPET ARE THICK THE VACUUM WILL PULL ITSELF TOWARD THE FLOOR SLOW DOWN THE BRUSHROLL ENOUGH TO TRIGGER THE AUTO SHUTDOWN ON THE MAGNESIUM BECAUSE THE VACUUM CANT BREATHE. TAKE IT TO YOUR LOCAL ORECK AND THEY CAN PUT A FEW HOLES IN YOUR SOLEPLATE AND THIS WILL TAKE CARE OF THE ISSUE.

try soaking the plate for a few minutes in ammonia ...it will bring these back to life

You need to shut it off, unplug it, and pull both the filters out at once and then plug it back in, and push both filters in at the same time, simultaneously. This will re-set it.
Also, if this continues to happen, you must vacuum the insides of the unit, aside from the filters, themselves, it can get all clogged up.
We live on a busy street and our house can get REALLY dusty, we have a older home with carpets and two cats - so our unit really has to work hard!
Good luck!