Engine running rough & stumbling, Normal after restart

[Greg Greer]

I cranked my 1986 3.2 Carrera 911 for the first time in about a month. The start up seemed a little rough running, but idle smoothed out. When I got on the road, the engine was down on power and stumbling. I drove it a little ways, got the engine warm, and varied the RPM to see if it would smooth out. It didn't. After returning home and turning the engine off, and then restarting it, the car is running normal again, good idle, and back to feeling strong. Any ideas what might be happening?
Thanks everyone for your of hard won experience, advice, and knowledge.

[dogslovetrucks]

Add your 911's year and engine either onto your signature or into your post.

[Gilbert456]

I'm happy to see a particularly subject.