Engine Starting Problems

I have a 2014 T100 with just over a thousand miles on the clock. Today it started fine. I did a six mile journey., left it for an hour then started it and did a short 2 mile journey. On restarting the engine it was just as if it had a flat battery and the engine hardly turned. Tried again and it span up as normal. Rode the couple of miles back. Left it for a couple of hours and it repeated the symptoms. Ran perfectly on the six mile journey home. Got home and it did the same but on some 6 attempts at starting it during this afternoon it started OK every time. Battery is showing just over 12 volts on my test meter. Question is what caused it and what should I be looking for tomorrow when I look over it? .

 

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Update on the situation: - It has started fine the last couple of days.
First time, every time.

I contacted my local Triumph dealer who did know of this clutch sensor problem but they also advised me to check the battery and I got the following readings on a standard dial type meter: -
At rest = 12.6V
Ignition On = 12.2V
On Start Up = 11V
They recommended spraying the sensor in the lever with a product suitable for electrical contacts..
Thanks for your answers.