Long version: so yesterday evening I plugged in my phone (a Samsung Galaxy S4 mini) while we were putting Matthew to bed, as I thought it was likely to be short of battery. When I came back to it it was off, so I initially assumed I'd just plugged it in badly and it had run out and was too low to even turn on. So I replugged it and gave it a bit longer, assuming it would then boot. It didn't.
When I switched to the upstairs charger it wasn't even making the light on the charger come on when plugged in. I tried holding down several buttons, and removing and replacing the battery, and eventually it admittedly to charging again and showed the charging icon on the screen, so I left it for a bit to charge.
When I tried later to turn it on though it failed to boot - it vibrates, shows the Samsung logo and model details, then pauses, then vibrates again as if to say it's shutting down and goes blank. It then repeats this over and over again until you give in and take the battery out again.
I googled a bit and tried rebooting it in recovery mode. This gets a bit further, you see 'recovery boot' in tiny blue letters in the top left, then it flashes a different screen so fast you can't really see it, then says 'no command' with a little picture of a robot lying on its back with its tummy open and a warning symbol.
I've contacted my insurers online as their phone is only available Monday to Friday, could be 48 hours to hear back from them, looking at cheap android phones online and not seeing anything that would do quickly as a short term replacement and future spare. Thank goodness for the iPad in the meantime. Might have to start carrying my iPod or camera or both around again :)