my MDS .40 does that a lot, its mainly if i try and start it at idle, i often add 2 or 3 clicks of throttle (enough to start it in forwards and give it a high idle but not enough to make it move the airframe) but now ive run it in a bit more and leaned it out it seems to be a bit better

if you are using your fingers - Your a numpty! get a chicken stick or an electric starter and make sure you have that plane tethered to something solid or restrained so if it does start up and try and take off you arent in the way