Janda,
My Pip is just the same, isn't it frustrating!
For me I've started having a shower when I put him down to nap - if he fusses a bit he's gotten over it when I'm out of the shower.
Try to put him down before he's actually tired? Like at the first slow blink or other tired sign? Maybe with a toy or rattle in his cot and he may fall asleep with it?

Good luck!
kaz