I’ve done a fair bit of mountain biking over recent years. A stupid question maybe, but is your ride height correct? If the saddle is set too low you will tug at the bars to get pedal arm leverage. Raising your seat ride height will put more weight forward and over the bars. Equally, if the bars are set too high you’ll have the same effect, so if your saddle height is correct and the bars are higher than the saddle try lowering the bars to saddle height.
Not a bad looking bike BTW.