Few minutes after starting alarm came on for 1 minute without indication

 

This happens to me occaisionally but not with the engine running.

If it happens again, if you switch off and remove and replace key in the ignition

that may stop it.

This Jag is prone to some funnies which appear from time to time and then do

not appear again for months or years.

 

Not sure what you mean by alarm. Sounds like it's the rear sensor indicator only.