If the boot was full of water the it’s more than likely that your junction box is slowly dying
It’s a box in your boot that holds relays, fuses and computery things
If it does turn out to be that, then it’s an expensive fix. Although I’ve read that some people claim to have fixed them by removing and drying them out. There are also people on the internet who say they can fix them
All I can say is good luck with this one