My bike started perfectly yesterday (like every day) but when I went to put it in garage after work I started it & thought it sounded sluggish so switched it off again, when I went to restart the best way I can describe it is when I pushed the start button the noise it made was 'trrrrrrr' like the starter wasn't engaging?

I put it away & when I went to start it later it turned over no problem.

What should I check to see if this will happen again?

Cheers

Check the charging system firstly.

Sounds like it could have a dying battery.