1993 Jaguar XJ6 - Ignition problems/Intermittent power loss

Hello everyone, I have a 1993 XJ6 with approx. 125k miles on it and lately there have been times where when I try to start the car when the engine's cold, there isn't any power at all. I turn the key and there's no lights or engine sounds....try immediately to start it again and it's fine (although I need to enter the code to use the radio). There have been other times where the engine would crank but won't turn over (however, this isn't as prevalent as the intermittent power loss problem). After letting it rest for a little bit, it will start fine and run with no problems.

Also, and it's only happened once, the car's power cut completely off while I was at a stop light, only to start back up again when I tried. Any ideas as to what the cause might be? Could all of these problems be tied to one thing? Any help is greatly appreciated! Thank you for your time.

Manzan