Westwood T1600 Engine cuts out then starts once 'rested'?!?

Hi. This Westwood T1600 has just been serviced and I have probably cut 2 acres since. It now keeps cutting out, has 'backfired' (?) a couple of times, and now needs to be left for 30minutes or so before starting again - and will then work for approx 5 mins before cutting out again! When refusing to start, it sounds a rapid 'click-click-click' noise and makes no effort to turn over. Gradually, you can hear it trying to turn over before it eventually starts......for a short time! Please help, I have another 5 acres to mow and at this rate I won't get it done before the winter!