I’m currently cruising over western China/southern Kazakhstan. I’m flying through 90 kt headwinds at M0.85 at FL350. With this headwind, I should be flying at about 410 kts ground speed, but I’m currently flying at 390 kts. The speed has been slowly decreasing for the past hour. On top of that, the throttle sometimes shoots up to 100% randomly, stays there for 10 seconds, goes down to 35-45% for 10 seconds, and then bounces back up to normal. What should I do?