A scorer of more than 240 goals at club level and for Scotland, he hit over half of the total at Celtic.
Griffiths has been working on his fitness six days a week, including with trainer Martin Clifford at a boxing gym, ready for the next opportunity.
He told the Sunday Mail: “It’s a difficult time just now as I see clubs going back for pre-season and wonder when is it going to be my turn?
“I’m not going to lie, it gets lonely. It knocks my confidence not having my future sorted. Six days a week I’m in training and all of this work will come to the fore when I get back onto the pitch. “
“I’m ready to go but when is that chance going to come, is it going to come?”
Griffiths still has “plenty more goals and targets" ahead of him as he targets his next move.
Last season there were questions about the striker's weight as he struggled to make an impact consistently at both Dundee in the Premiership and then with Falkirk as they toiled in the third tier once more.
He has revealed he has lost five kilos as he looks to get down to his fighting weight of 73kg.
“I wish I’d done this type of training earlier in my career and if I’d done more in the off-season I wouldn’t be in this position,” Griffiths said. “I’m now a free agent and hopefully I’ll be back scoring goals shortly.
“I’ve lost 5 kilos so far but I’ve never been heavy even if other people would disagree with that and I still have a bit to go as I want to lose another two kilos. My best weight is 73 kilos, when I had my best scoring season at Celtic I was around 72-73 kilos.”