Engine light blinking continually, rough running
 

2002 Sable, 108,000 miles car has been working fine. Got out of car for a short while and when started again the Check Engine lite started blinking continuelesly. No code blinking. Engine was now running rough. Could travel a 60mph and could feel slight hesitation. When stopped it felt like it would die but it didn't.

One shop said plugs or coil. Another shop said compression in #3 cylinder is at 30 pounds and recommends replacing the engine as it is cheaper than rebuilding the engine. No evidence of oil burning.

what puzzles me is why the engine runs fine until it is started again. At 30 pounds compression I would think that this would have been noticed over time.

You thoughts are appreciated.

Ask the shop that says your engine is shot to show you the numbers where they did the compression test. They won't, because they didn't. Then go to another shop and have them run a code scanner. The system is set up to give the operator a rough diagnosis of what is wrong. When that shop fixes the problem, make sure you tell everybody about your experience at both shops.
Gator