I have recently experienced some problems with ATC directions when flying from Newcastle to Manchester and Newcastle to Blackpool. What happens part way into an IFR flight is that the ATC directions keep switching between two headings at about one minute intervals. When I look at the map I see the flight path forms a near perfect sine wave about the desired track. Eventually it seems to break out of this bahavior and correctly direct me to the proper heading for an ILS approach to the correct runway but in the mean time it makes for a very busy cockpit. Does anyone have any idea why this is happening?

Iis just the engine trying to get itself sorted out, it does it all over the place, but as you see it eventually gets it right. Keeps you on your toes.