We need a lot more information in order to help you.
What OS, what version of AE, what system specs, etc.
Yeah, this could definitely be a ton of things. First question however from me is, is it related to one particular project or does it affect all of them?
And not to get ahead of things but if it IS just centered on one project then I'd look in the folder it creates where you were saving them for autosaves and see if an earlier saved version might open.
That would at least narrow it down to a problem with a specific project version.
However, forget all of this if it locks up on every project and provide the info that Szalam asked for for further diagnosis.
I am having the same problem with both premiere & after effects. I would launch them and it would go just a little bite the FREEZE!, no errors, no NOTHING!. So I just backward both to the first update for 2017, and at this point, I am having no problems.
So I suggest go backward's and see what happens!.
The first thing to do when you encounter an unexpected problem on launch is to reboot, then engage the caps lock key and try and open AE, then open a project. if you get failures then it's time to start checking to make sure that no other apps are running. Be wary of virus scanners and network settings. If all else fails you can try deleting the preferences files.
I hope this helps.
OK, so I thought that going backward's with the software updates would help, but that didn't work with AE, but it did seem to work with Pr. As for Ae it still froze on me this morning, so I had to reboot my system. Rebooting the system always helps and I am able to launch Ae, but having to re~Boot every time just to get into your program is ridiculous and a waste of time. I do remember that back a few months ago I never had these problems.
Well I guess I was wrong, so I did find this Adobe Creative Cloud Cleaner Tool, and it seems to have taken care of the problem at this time, but time will tell!.
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.
You might also check the responses here, as well. One customer solved their issue by running the Adobe Cleaner tool. You might try it.
Sorry, I didn't get back sooner, but I did resolve my problem. I ended up doing a quick reinstall/fix of my windows as it seems some of my profile folders were all screwy, so after I did this and re-Install after effects, it all worked out. So thanks, all who helped me.