Vauxhall Astra cold start

When starting the car from cold:
The temp gauge goes up to 100. The fans come on. there may be a slight uneveness in the running.
After a couple of minutes-when moving-it all returns to normal and there is no recurrance. I have left it for two hours and it still does not recur.

I have had this car one day. Known problems are:
Air con-may have a leak.
Clock display-dim, temp etc okay.
Drivers side sidelight dimmer than passengers side.

I think there may be an electrical problem somewhere which I shall start investigating but in the meantime does anybody have any ideas?

Thanks in advance

Andrew