Yes, I think for us it's because she's overtired. It's a vicious cycle because when they get too tired they don't sleep which only worsens their tiredness. We're holding/rocking/bouncing her in our arms for about 10 minutes past when she falls asleep then moving her to her swing. She seems to be sleeping better today with this approach but we'll see how it works long term.
If it's a new thing for your LO it might just be because of a growth spurt, I've heard there is one sometime between 6 & 8 weeks which might affect his sleep.