No idea about the cruise control, but here is an idea to get more responses. Rename the thread to read something like: "My Cruise Control works when it feels like it. Any ideas?" C/C is very enigmatic and sure, that may get someone to click, but a totally random person (like myself), not anyone who actually knows anything about the issue at hand.
Replace the cruise control switch. If any other steering wheel controls are marginal then replace the “clock spring” wiring harness behind the steering wheel hub.