*Don't post only hastags
*Your account must have email address not just your phone number
*Don't follow more than 1000 daily
*Don't send messages more than 1000 daily
*Don't use such autofollowers websites or apps
About a month ago my twitter account was also suspended. The reason twitter mentioned was "Auto Bot".
Later I tried to recover my account but I was not receiving the sms authentication code and I was unable to do further actions to gain my account back.
At that time I noticed Twitter sent me an email also which was associated with my account - then I appealed from their and recovered my account within few hours I think.
I wrote in my appeal that it is true I do a lot of tweets and retweets but I'm not using any kind of bots - please recheck from your end and give my account back.
Twitter has a bot which checks for bad accounts and suspends automatically, they might be using it very often.
In your case,
* Posting hashtags isn't an issue I think because I'm still using hashtags.
* Agree
* If you did this then you were spamming.
* If you did this then you were spamming.
* It seems Twitter doesn't like auto bots for any kind of use. So everyone should ignore.