My apartment has several problems - are these all related?
1st: The bathroom cold water supply - never the hot water - gets repeated airlocks, especially if I take a bath instead of a shower or if the shower is longer than usual. I can connect up the kitchen supply and force the airlock back into the cold storage tank which usually solves the problem. Lately the solution is only temporary and a few hours later the bathroom cold water stops again.
2nd: the toilet is constantly dripping after flushing.
3rd: the heating/hot water supply has been very variable recently even though the boiler has been checked out and is OK.
-- Could all this be related? Thanks for any advice.

The toilet has 2 valves in it. It will run if either are dirty or worn. Check them out. Toilets are carefully built to prevent water from being drawn out of the tank into the pipes, antisyphon. Fix the valve, and you may fix the air lock problem.