MG MIDGET ENGINE SYMPTOM

My Mg Starts Up Good It Runs For About 20 Minutes And It Shuts Off Itwornt Atart Back Up Untill You Let It Set For 15 Or 20 Minutes It...

I Have A 73 Midget In Good Shape. It's Been In The Backyard For A Few Months And Has Started Each Time I Tried. Now That I Need To Move It...