Timon is a wealthy guy who lives like a rock star. He throws lavish parties to impress his friends, but can't handle his own finances. Several people - including his own accountant - tell him that if he doesn't pay his bills soon, he'll end up broke. So he pre-emptively gives away his fortune to his friends - and then almost immediately starts hitting them up for money. He rationalizes this as testing to see if they're 'real' friends, but I think it's really just a continued ego/power trip. As Flavius points out, Timon has lived his whole life at the extremes of wealth and poverty, but has no experience negotiating the middle ground.
One thing that's unusual for Shakespeare: There are almost no women in 'Timon'. Except for Phrynia and Timandra, all of the characters are men. Probably explains why Timon's home is like a frat house.
I have some pity, but not too much sympathy, for Timon's character. He gives away money that's not really his to give in the first place, and then asks for it back. No wonder his friends have no respect for him.
The other thing that interested me about Timon was how he reminded me of Lear. Like Lear, Timon is a man of means who feels burdened by his wealth, and seeks to unburden himself by giving it all away. Like Lear, he imagines that he will be able to prevail upon his beneficiaries to help him out of his own self-inflicted poverty, and feels betrayed when they do not. Like Lear, he finds himself exiled to the wilderness. And as with Lear, there is a sympathetic party who mounts an attack on his own territory on his behalf - although in Timon's case, Alcibiades' attack on Athens is initially motivated by reasons unrelated to Timon, and the goal is not rescue but revenge.
I'll have to watch it again. I think I'm relating to 'Timon' more personally than to most of Shakespeare. I know how difficult it can be to stay on that stable, middle course - and what it's like to live around someone who never finds it.