According to Nvidia, Shield tablets in question were sold between July 2014 and July 2015 and is asking users that might have such a device to stop using it, except in order to participate in the recall or backup their data.
At its dedicated recall website, Nvidia notes that users should make sure that the device is updated to the last software version and then check if their device comes with either Y01 or B01 battery. Those with Y01 battery can then participate in the recall and will be receiving a replacement tablet after registering at the site.
Nvidia was quite keen to note that the recall does not affect any other Nvidia products and hopefully the affected batch of Shield tablets is not that big.
You can find all details regarding the recall at the dedicated Shield tablet recall site.