On cars with stop start buttons I think its usually close to the button. . Otherwise they are typically near any steering lock.
But if its only just started happening thats probably not the issue,at least not directly. It may need expert attention.
If you havnt already done so it may be worth carefully reading relevant areas of the owners manual, which may offer a clue. I have in the past owned a car years before finally discovering some obscure electrical switching option to do with keys, security systems ,central locking etc.