Laptop sometimes not going to sleep

My laptop is sometimes not going to sleep. You can see it looks like it's about to then just as all the lights go out, they come back on again. It's like something is waking it, just after it sleeps.
Anyone come across this before?
Is there a way to send it to sleep from the command line to see what's going on? Similar instruction to shutdown -h now bit for sleep rather than shutdown.
Thanks.
Anyone come across this before?
Is there a way to send it to sleep from the command line to see what's going on? Similar instruction to shutdown -h now bit for sleep rather than shutdown.
Thanks.