K11 temperature needle high and no hot matrix air

I have a slight issue with my K11 Micra, been driving fine, then tonight I noticed the heather matrix blowing cold air on hot, then temperature needle going high sometimes slightly into the red, but didn’t overheat. The fan doesn’t seems to kick in and then the needle goes slightly down then the needle rises again
Coolant levels are ok, and both top and bottom hoses hot.
Is this an air coolant airlock
Any advice?
Sorry I forgot to update the thread.
Basically, a minor leak at the bottom pipe, which now tightened the jubilee clip, the rad got low and created an airlock. Topped rad up ran it without the cap on, (there was a few air bubbles), then put the cap on fan came on and it seems to be all ok at the moment!