There are 3 players in my group. One, who is just beginning with roleplaying games. Second one, who has been playing multiple systems for a few years. Third one, who probably has been playing for more than 12 years. Surprisingly, the most problematic is the second one.
He is constantly overthinking pretty much everything. He plans what to should they, or how to do something in every possible scenario. Sometimes it takes him nearly an hour to decide over options a), b) or c). It really kills the mood. The rest of the players are getting bored and go out of the atmosphere, that I have been creating since the beginning of the session.
For example it took him literally 50 minutes to decide if they should:
look for one of the 13 artifacts, which collected together grant UNLIMITED POWER
kill one of 9 mages, helping BBEG who wants to get all of the mentioned artifacts (he has already 8 of them) and conquer every piece of land
find wife of one player, who had been looking for her for 7 years
deal with a powerful Doppelganger who is holding the mentioned player's daughter captive
destroy an organisation, which goal is to kill all the players, the BBEG and every single avatar(those who have blood of the deities)
Suggestions from the other players didn't help a lot, because he is always uncertain if his choice is the best one possible.
After deciding on the first option, he spent yet over half an hour coming up with lots of hypothesises, about what should be done in specified, highly unprobable situations. I know, that having no plan isn't a smart, but this is just as bad, or even worse.
I don't want to make the campaign linear, as I dislike such adventures and I want to let my players do whatever they want. Changing the way the game is going on is not what I want to do.
What can I do about it, to make my game more fluent? Of course kicking out the player is not even a thinkable option. I have tried to set time limits. "2 minutes passed in combat and once again you can't decide on what spell you want to cast? You loose your turn." This helped to keep up with the rhythm of combat, but on the other hand caused a lot of pressure. Conclusively he got very nervous and irritable.
He has already changed his character three times, among way differentating ones, like a telepath psionic or chameleon(universal class, that can do a little this and that).