Just over a week ago I came back to my car (Fiesta mk7 09 1.4 tdci ~50k miles) to find the remote fob not working to unlock the car. Assumed the fob battery had died, so unlocked manually via the key. Got in the car, realised there was absolutely no electrical power, completely dead, no dashboard/interior lights, turning key in ignition did nothing.

Assumed the battery had randomly died. Checked under bonnet for connections etc., all seemed fine. Was about to call break down, then suddenly all power came back and I was able to start the car. Assumed it was some electrical glitch, didn't think much of it.

All fine been driving as usual all of last week until today - came back to car, unlocked fine, all power fine and then electrics go completely dead just as I'm turning key to start engine. Thought I was scuppered this time, but then suddenly, again about 5 minutes later, all power came back and I was able to start engine and drive home fine.

I noticed both times the clock had lost about 5 mins of time, so I assume somehow using the key fob in the first instance was what caused the power cut? I can't think what the problem is, the battery should be perfectly healthy as it was replaced only a couple of years ago. I don't know much about these things, but perhaps an issue with the alternator? Or just battery connections/terminals?

In any case, it probably needs a trip to the garage but I thought I'd ask here if anyone has any idea what the problem might be and if there is a simple fix that could be tried? In the meantime I assume I am ok to drive the car until it goes into garage (if it comes to that) - I'm worried now that the electrics could go dead while driving which I don't think would be a pleasant situation to be in!

Thank you in advance for your help.