There are some shape sequences for which I can't find an answer or the reason for the given answer. Can I ask them? However, then I don't know what title to use for each cause they are all like "What is next in this sequence"
Can you? Yes. Should you? Probably not.
"What is the next in this sequence" patterns are often poorly-received. If you do decide to ask a lot of these, you will likely be heavily downvoted. (Also, keep this in mind: If you're getting these from somewhere else, you must have permission, and you must say where they come from.)
Enjoyable puzzles naturally lead to unique titles, based on the aspect of the puzzle that makes it enjoyable - the part that makes it interesting. If you can't think of a unique title to give your puzzle, that is a clear sign that the puzzle is boring. It won't be fun for people to solve, and it likely won't get a good reception.
To answer your actual question ...
Yes, these puzzles are on-topic.
As Deusovi says, it's not advisable to post loads of them in quick succession - they won't get closed, but they'll likely get a lot of downvotes if you do that. People will soon get bored of a long sequence of similar-looking puzzles, even if each one on its own is perfectly valid. But that's the point: each one is perfectly valid. As long as there is a unique and verifiable solution (as there should be to any puzzle), asking for the next in a sequence of images is an OK puzzle and possibly even a good one. Just don't go over the top with them and you should be fine.
Title them as distinctively as you can.
Every question should try to have a distinctive title, so that you can tell roughly what it's about just from a quick glance at the title. We don't always succeed in doing this - it's been a problem for a long time here on Puzzling; see Non-descriptive titles, Informative titles for rebus puzzles, Titling Overhaul, etc. - but we should at least try. I've made a LOT of edits over the years to give puzzles more descriptive titles than things like "What am I riddle" or "Another rebus puzzle".
How to do this will depend on the nature of the puzzle; I can't really give you much generic advice. If you're asking about a sequence of letters or numbers or words, put at least some of the sequence into the title. If you're asking about a sequence of images, maybe at least try to describe the images in the title? "What's the next in this sequence of boxes filled with black and white balls", for instance.