Can one set the alarm on cell phone to vibrate on shabbos? Also, can one move it away after it “rings”, is there any issue of muktzah?
One may set an alarm clock to ring on Shabbos, however you have to put it in a place that you will not inadvertently turn it off when you half way in your sleep. Therefore put it somewhere not near your bed. After it rings you are technically allowed to move it if it disturbing your use of the room, (you want to sleep move, and it is disturbing you) since it is considered a kli shemilachto l’issure, which may be moved l’tzorech mikomo. Otherwise you cannot move it. Even if you have to move it, you must be extremely careful that you don’t touch it in a way that will cause the screen to turn on, etc.
Sefer Tiltulei Shabbos response from R’ Moshe Feinstein zt”l-8, and From R’ S. S. Z. Auerbach zt”l- 4.