Starter engaged - stuck ON

I only seem to have this problem when it's cold outside, but when I turn the ignition key to start the 633, the car still starts immediately but the starter stays engaged for longer than it should. I thought it was the ignition switch, so I backed the key off after ignition but doesn't change anything. It seems that the starter itself stays engaged until the spinning engine knocks it loose.

Anyone know if this is a common problem with 633's? (1983)

Thanks.

the solenoid or a the flywheel or improper simmed. Have it diagnosted by a mechanic