hayleywaley my ds1, now nearly 4, was just like this. I couldn't leave him with anything for a minute. He wasn't even happy being held unless the view was changing every 2 minutes. I nearly went nuts.
If it helps(!) he is still like this- really easily bored, to the extent that I have asked his school if he might have ADHD! but they said they don't think so, he is just very sociable but also self-motivated and wants to control all his own activities. For instance, he will spend an hour now (if accompanied by an adult!) doing a puzzle magazine with sums etc in it, but will rarely sit and draw a picture. Baking with him is a nightmare- he just starts mucking about and shouting, pulling silly faces etc. He wants to follow adults around with him, talk constantly, and ask questions all day (hence my name on here!) But he can behave impeccably in a restaurant if he wants.
I suspect your boy will have some of these traits and is obviously very active, just like mine. It's really hard work, but I think these strong, (hyper)active characters are often also charmers and really sociable.
For now, I think you have to just put up with as much crying as you can- i never found a way to make ds1 less bored other than going out and taking him to new places all the time. When he could walk and talk, it was so much easier although exhausting.
I sometimes found his crying was overtiredness too as he couldn't switch off, and if I left him (out of despair, as needed to eat, go to toilet, etc) he would sometimes fall asleep.