This particular transfer case has a lot of design flaws and is used in GM and Chrysler trucks. I’ve experienced similar problems that just magically went away. The t-case actuator, the sensor in that actuator and the switch are all common problems. The cheapest and easiest to replace is the switch. As the miles accrue, watch for oil spots colored blue from the middle of the truck. This indicates the oil pump inside the transfer case chewing its way out of the case. The pump wears the softer case and creates a leak. The prevention is to remove, disassemble and install a wear washer into the case. Once it leaks, it can be repaired with epoxy or replace the case. Either way, get prepared for a big repair bill.