Not with motivation, that thing is rather fleeting and unstable. Though not only forcing it with discipline, that's a rather limited resource as well.

Basically using as little discipline as possible to slowly form a habit.

So now you're going at least once a week, good work. Keep it going until it becomes a habit, few weeks to months. Once that has become a habit, add in another day and repeat the habit forming process.

It took me nearly a year to go from once a week to 5 times a week and by now during winter i can add in cardio sessions as well and up the frequency easily to 7 days a week.