I think that the chances are very good that this may be your issue. To test this for no additional cost, try for the next 2 weeks, using only an ignition key and nothing else on the ring. If it stops, then you can be certain that this is your problem. Here is a copy of the bulletin from GM regarding the key issues.
#05-02-35-007A: Information on Inadvertent Turning of Key Cylinder, Loss of Electrical System and No DTCs - (Oct 25, 2006)
This bulletin is being revised to add a model year. Please discard Corporate Bulletin Number 05-02-35-007 (Section 02 - Steering).
There is potential for the driver to inadvertently turn off the ignition due to low ignition key cylinder torque/effort.
The concern is more likely to occur if the driver is short and has a large and/or heavy key chain. In these cases, this condition was documented and the driver's knee would contact the key chain while the vehicle was turning and the steering column was adjusted all the way down. This is more likely to happen to a person who is short, as they will have the seat positioned closer to the steering column.
In cases that fit this profile, question the customer thoroughly to determine if this may the cause. The customer should be advised of this potential and should take steps to prevent it - such as removing unessential items from their key chain.
Engineering has come up with an insert for the key ring so that it goes from a "slot" design to a hole design. As a result, the key ring cannot move up and down in the slot any longer - it can only rotate on the hole. In addition, the previous key ring has been replaced with a smaller, 13 mm (0.5 in) design. This will result in the keys not hanging as low as in the past.
Part Number
Description
15842334
Cover, Dr Lk & Ign Lk Key
Chevy Technician
GM Grand Master Technician 2007. 9 years Automotive experience, 7 years with GM. Just Answer Mentor