Can painless muscle twitches in the body. could it be a brain tumour? ?

Probably not: Fasciculation or "muscle twitch", is a small, local, involuntary contraction and relaxation with a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons. They are encountered by virtually all healthy people, though for most, it is quite infrequent. In some cases, the presence of fasciculations can be annoying and interfere with quality of life.