My advice: Don’t. Instead, push yourself to walk 30 minutes 3 days a week. Then 5 minutes of running, 25 minutes of walking, then 10 minutes, etc, etc.

There’s absolutely nothing wrong with starting slow. In fact, I’d argue it’s by far the best way to start. When you’re first starting something, it’s almost never necessary or desirable to push yourself to the point of failure, or even significant discomfort.

When I started lifting weights, I estimated what I could actually lift for reps, and started out doing half of that much. When I recently re-started running after several years off, I knew I could do 3 miles at 8:00/mi. I started by doing 1 mile at 12:00/mi. I recently ran my first half-marathon. Slow and steady wins the race, because slow and steady actually makes it to the end.