Put in two starters in two years. This winter started having trouble when driving car - occasionally when I hit a bump in the road the radio and wipers cut off and if I pull over and restart the car they will come back on. My mechanic thought it was due to a loose battery cable and he tightened it up but, it is still happening. Also noted - when starting occasionally I hear a e-e-e-rk sound (I think the ignition) and if I turn key to off and try again it usually starts - sometimes it takes 2-3 tries.
I suspect that the trouble may be with the ignition switch ACC contacts. Try moving the key slighty back and forth when the trouble happens, but not enough to change the actual switch positions, and see if that changes things. If it does then you have pretty much proved it. This trick might work for you but even if it doesn’t I suspect that the switch is causing the trouble.
Try using just the ignition key without anything hanging on it. To much on the key ring pulls on the ignition switch and could put it in ACC, just ask GM.