It would be way easier to simply delay requests for a certain amount of time (say 4 minutes or so).
You can find that option in the Request Policy Config.
If you really need a PAL to monitor the queue wether two adjacent tracks are both requests, you'd have to run a PAL that's always on and checks the first two queue items if they were requested.
This one should work.
VAR first, second : TSongInfo;
PAL.Loop := True;
first := Queue.NextInQueue;
second := Queue.NextInQueue;
IF (first['requestID'] > 0 AND second['requestID'] > 0) THEN