"tentatively started" is a correct and usable phrase in written English.
You can use it when you want to express that something has begun, but with uncertainty or tentativeness. For example, you could say, "We tentatively started planning our vacation this weekend."
On bishops and laymen tentatively starting, after Vatican II, to organise things their own way, he strenuously imposed obedience to the diktat of the Holy See.
You tentatively start the film knowing you won't be able to sleep for weeks or shower without fearing what might be lurking behind the curtain.
12. Fox cubs In the next few weeks fox cubs will begin to emerge from the earths where they have been born and tentatively start exploring the world outside.
Crew Dragon is one of two spacecraft, each capable of carrying seven people, that will transport U.S. crews to and from the ISS, tentatively starting in 2017.
Meanwhile, Benioff's contemporaries are tentatively starting to act and speak out against Trump, as liberal activists pressure businesses to take a stand.
"And then can we make a song?" one of the girls asks irrepressibly, "And we'll be famous?" "Well... .. the man, a little tentatively, starts to agree.
Many journals are tentatively starting to experiment going down a partially more open route, but from our positive experiences so far we would encourage them and others to be bold and embrace full transparency.
He gave her a key to his flat; tentatively, she started leaving overnight stuff there.
Rather tentatively, Mr. Buffett started to talk about the economy, and Mr. Byrne defended his decision.
Tentatively, we start to climb the 1,200 steps – thin shards of stone stabbed into the hillside – that lead to Teyuna.
