Remote unlocking

[Dr Jekyll]

I tried to unlock my XE this morning and had to resort to the mechanical key because the remote didn't work. After a few minutes drive I parked and tried again and all was fine. Is this a key issue or a car issue? The spare key didn't work either, but then didn't work after the problem had gone away so I don't know what to make of that. Can it occur as a temporary glitch or do I need something fixed?