Starting pedaling from a stopped position is suddenly very difficult.

Recently, I've noticed that from a stopped position I try and pedal and hold the 'go' button down and the pedaling is extremely difficult. Can't get enough momentum for the electric motor to engage for a few seconds and it's becoming a bit of a hazard (light changed green and I'm trying to go but the pedal action is super tough).

I'm not sure why this happened suddenly, when I pick up the back of the bike and use the pedals it has low resistance, so I figured the front wheel nut was too tight, I loosened it a bit last night (hand tight) and it helped a little bit, but it's still super difficult to start pedaling from a stopped position.

Is this a known issue or common? my ideas what to try to alleviate and get the bike back to normal?

Thanks