There really is not much you can do without voiding your warranty. This may be something simple like a connector that vibrated loose inside the control panel. (Alternator to contol panel inter-connect) There could also be a wire lying loose that was not connected. Open the control panel... and look for anything obviously out of place. DO NOT do anything else. After that your stuck with the warranty process of Briggs and Stratton.
When your at a B & S service / repair point... (store front)
Things to note .
1. Tell servicer unit is for PRIVATE USE (There is no warranty for commercial use)
2. Have proof of purchase in hand otherwise they will use the MFG date as the start point of the warranty. Many generators sit in a warehouse or on the shelf long past an implied warranty (date of mfg) Bottom line you need to have your sales slip.
There are several things I could have you do but... as the consumer the only thing you can do is perform an inspection. By opening the control panel you need to tell the servicer the only thing you did was a VISUAL Inspection......
Anything else will void your warranty.
So.. look for any obviously loose parts or or connectors. After that sadly your stuck with dealing with warranty service.
Thanks for choosing FixYa,